Smart and Flexible Energy Devices

Cover
Half Title
Title Page
Copyright Page
Contents
Preface
Editors
Contributors
1. Smart and Flexible Energy Devices: Principles, Advances, and Opportunities
	1.1 Introduction
	1.2 Flexible supercapacitors
		1.2.1 Flexible supercapacitors based on carbon
		1.2.2 Flexible supercapacitors based on metal oxides and sulfides
		1.2.3 Flexible supercapacitors based on nanocomposites
	1.3 Flexible batteries
		1.3.1 Flexible Li-ion and Li-sulfur batteries
		1.3.2 Flexible metal-air batteries
	1.4 Flexible proton exchange membrane fuel cells
	1.5 Flexible solar cells
		1.5.1 Dye-sensitized flexible solar cells
		1.5.2 Perovskite-based flexible solar cells
	1.6 Conclusion
	References
2. Innovation in Materials and Design for Flexible Energy Devices
	2.1 Introduction
	2.2 Materials
		2.2.1 Inorganic nanomaterials
			2.2.1.1 1D materials
			2.2.1.2 2D materials
		2.2.2 Organic materials
			2.2.2.1 Polymers
			2.2.2.2 Other organic materials
	2.3 Structural requirements
		2.3.1 Flexible substrates and membranes
		2.3.2 Thickness of compound/active layer
	2.4 Wearability assessments
		2.4.1 Softness
		2.4.2 Stretchability: The residual strain
	2.5 Self-healing mechanism
		2.5.1 Intrinsic self-healing polymers with reversible bonds
		2.5.2 Self-healing through exhaustion of healing agents
	2.6 Design of flexible energy devices
	2.7 Flexible energy storage and conversion devices
		2.7.1 Energy conversion devices
			2.7.1.1 Nanogenerator (NGs)
			2.7.1.2 Photovoltaic
			2.7.1.3 Other flexible generators
		2.7.2 Energy storage devices (ESDs)
			2.7.2.1 Flexible batteries (FBs)
			2.7.2.1.1 Li-ion flexible batteries (LiBs)
			2.7.2.1.2 Other flexible batteries
			2.7.2.2 Supercapacitors (SCs)
	2.8 Configuration designs for flexible ESDs
		2.8.1 1D configuration of ESDs
			2.8.1.1 Fiber-type
			2.8.1.2 Spring types
			2.8.1.3 Spine type
		2.8.2 2D configuration of ESDs
			2.8.2.1 Layered sandwich configuration
			2.8.2.2 Planar interdigital configuration
			2.8.2.3 Other 2D novel configurations
		2.8.3 3D configuration ESDs
			2.8.3.1 Origami/Kirigami/honeycomb-based structures
	2.9 Summary
	References
3. Basics and Architectural Aspects of Flexible Energy Devices
	3.1 Introduction
	3.2 Nanotechnology for flexible energy devices
	3.3 Architectural concepts, structures, and materials for flexible solar cells
		3.3.1 Flexible dye-sensitized solar cells FDSSCs
			3.3.1.1 Structure design and basic concept
			3.3.1.2 Flexible materials and fabrication process for FDSSCs
		3.3.2 Quantum dot synthesized solar cell (QDSSCs)
			3.3.2.1 Structure design and basic concept
			3.3.2.2 Flexible materials and fabrication process for QDSSCs
		3.3.3 Toward other flexible photovoltaic technologies
			3.3.3.1 Inorganic materials based flexible solar cells
			3.3.3.2 Organic materials based flexible solar cells
	3.4 Architectural concepts, structures, and materials for flexible batteries
		3.4.1 Lithium-ion batteries (LIBs)
			3.4.1.1 Structure design and basic concept
			3.4.1.2 Flexible materials for LIB structures
		3.4.2 Zinc-ion batteries (ZIBs)
			3.4.2.1 Structure design and basic concept
			3.4.2.2 Flexible materials for ZIB structures
		3.4.3 Flexible batteries advancement
	3.5 Architectural concepts, structures, and materials for flexible supercapacitors
		3.5.1 Structure design and basic concept
		3.5.2 Flexible materials for SCs structures
	3.6 Conclusion
	References
4. Characterization Techniques of Flexible Energy Devices
	4.1 Introduction
	4.2 Characterization techniques for flexible energy devices
		4.2.1 Scanning electron microscopy
		4.2.2 Transmission electron microscopy
		4.2.3 X-ray diffraction
		4.2.4 Cyclic voltammetry
		4.2.5 Galvanostatic charge-discharge test
		4.2.6 Electrochemical impedance spectroscopy
		4.2.7 Atomic force microscopy
		4.2.8 Secondary ion mass spectroscopy
		4.2.9 Inductively coupled plasma-mass spectroscopy
		4.2.10 Fourier transform infrared spectroscopy
	4.3 Summary
	References
5. Micro- and Nanofibers-Based Flexible Energy Devices
	5.1 Introduction of nanofibers and microfibers
		5.1.1 Carbon fibers
		5.1.2 Biopolymer fibers
		5.1.3 Aramid fibers
		5.1.4 Ceramic fibers
	5.2 Flexible energy devices based on nanofibers
		5.2.1 Inorganic fibers for flexible energy devices
		5.2.2 Metallic fibers for energy devices
		5.2.3 Carbon-based fibers for energy devices
		5.2.4 Biobased fibers for energy devices
			5.2.4.1 Cellulose-based fibers
			5.2.4.2 Keratin and chitin fiber composites
	5.3 Electrospun fibers for flexible energy devices
	5.4 Conclusions
	References
6. 3D Printed Flexible Energy Devices
	6.1 3D printing technologies
		6.1.1 Direct ink writing
		6.1.2 Fuse deposition modelling
		6.1.3 Material jetting
		6.1.4 Binder jetting
		6.1.5 Directed energy deposition (DED)
	6.2 Configuration of flexible energy device
		6.2.1 Active materials
		6.2.2 EES electrodes
		6.2.3 Electrolyte and the solid-state devices
		6.2.4 Configuration of EES devices
	6.3 3D printed EES devices
		6.3.1 3D printed electrodes
			6.3.1.1 Carbon-based electrodes
			6.3.1.2 Polymer-based electrodes
			6.3.1.3 Others
		6.3.2 3D printed electrolytes
		6.3.3 3D printed device
	6.4 Summary and outlook
		6.4.1 Precision and resolution of 3D printing
		6.4.2 New materials
		6.4.3 Integration with multi-materials printing technology and the interface
		6.4.4 4D printing
	References
7. Environmental Impact of Flexible Energy Devices
	7.1 Introduction
	7.2 Technical description of flexible devices
		7.2.1 Energy conversion devices
			7.2.1.1 Flexible solar cells
		7.2.2 Energy storage devices
			7.2.2.1 Flexible supercapacitors
			7.2.2.2 Modern designs of lithium-ion batteries
	7.3 Flexible materials environmental effects
		7.3.1 Cadmium
		7.3.2 Amorphous silicon (a-Si)
		7.3.3 Copper indium gallium diselenide (CIGS)
		7.3.4 Lead halide
		7.3.5 Carbon-based nanomaterials
		7.3.6 Tellurium and indium
		7.3.7 Toxic flexible substrate
	7.4 Processing routes and design strategies for safe and sustainable manufacturing
		7.4.1 Toxic materials replacement
			7.4.1.1 Lead-free perovskite
			7.4.1.2 Indium
		7.4.2 Improving processing routes
		7.4.3 Recycling
		7.4.4 Encapsulation
	7.5 Conclusion
	References
8. Metal Oxide-Based Materials for Flexible and Portable Fuel Cells: Current Status and Future Prospects
	8.1 Introduction
	8.2 Current architecture and materials for flexible and portable fuel cells
	8.3 Material challenges for flexible and portable fuel cells
	8.4 Strategies to Tailor metal oxides for fuel cells
		8.4.1 Morphological control
		8.4.2 Phase structure engineering
		8.4.3 Oxygen-vacancy control
		8.4.4 Doping
		8.4.5 Compositing with carbon/metal-based materials
	8.5 Current status of metal oxide-based materials in flexible and portable fuel cells
		8.5.1 Metal oxide-based catalysts
			8.5.1.1 Simple metal oxides as catalysts
			8.5.1.2 Perovskites as catalysts
			8.5.1.3 Spinel oxides as catalysts
		8.5.2 Metal oxide-based co-catalysts
		8.5.3 Metal oxide-based catalyst supports
		8.5.4 Metal oxide-based electrolytes/membranes
		8.5.5 Metal oxide-based bipolar plates and substrates
		8.5.6 Metal oxide-based current-collector
		8.5.7 Metal oxide-based electrodes
	8.6 Future avenues for metal oxide systems in empowering flexible and portable fuel cells
	8.7 Acknowledgments
	References
9. Flexible Fuel Cells Based on Microbes
	9.1 Introduction
	9.2 Basics of MFCs
		9.2.1 Instrumental bases
		9.2.2 Two-compartment MFCs
		9.2.3 Single-compartment MFCs
	9.3 Flexible MFCs
		9.3.1 Electrodes
			9.3.1.1 Carbonaceous material
			9.3.1.2 Bacterial cellulose
			9.3.1.3 Graphene sheet
			9.3.1.4 Polypyrrole (PPy)
		9.3.2 Membrane
		9.3.3 Microorganism
		9.3.4 Fabrication
		9.3.5 Applications
			9.3.5.1 Energy harvesting
			9.3.5.2 Treatment of wastewater
			9.3.5.3 Sensors and portable power machines
	9.4 Future aspect
		9.4.1 Large-scale uses
		9.4.2 Anode manipulation
		9.4.3 Membrane-free MFC
	9.5 Conclusion
	References
10. Flexible Silicon Photovoltaic Solar Cells
	10.1 Introduction
	10.2 Classification of flexible photovoltaic solar cells
		10.2.1 Inorganic flexible photovoltaic solar cells
		10.2.2 Organic flexible photovoltaic solar cells
		10.2.3 Hybrid flexible photovoltaic solar cells
	10.3 Flexible silicon (Si) photovoltaic solar cells
		10.3.1 Flexible crystalline silicon solar cells
			10.3.1.1 Recent progress in flexible crystalline silicon solar cells
		10.3.2 Flexible thin-film amorphous silicon solar cells
			10.3.2.1 Recent progress in flexible amorphous silicon solar cells
		10.3.3 Silicon nanostructures for flexible solar cells
			10.3.3.1 Silicon nanowire flexible solar cells
			10.3.3.2 Silicon nanopyramid solar cells
			10.3.3.3 Silicon nanoparticles for solar cells
			10.3.3.4 Silicon ink-based solar cells
	10.4 Outlook and conclusions
	Acknowledgement
	References
11. Flexible Solar Cells Based on Metal Oxides
	11.1 Introduction
	11.2 Substrate materials in flexible solar cells
	11.3 Flexible dye-sensitized solar cells based on metal oxides
	11.4 Flexible organic solar cells based on metal oxides
	11.5 Flexible perovskite solar cells based on metal oxides
	11.6 Other flexible solar cells based on metal oxides
	11.7 Conclusion
	References
12. Inorganic Materials for Flexible Solar Cells
	12.1 Introduction
	12.2 Inorganic photoactive devices
	12.3 Cu(In,Ga)Se2 (CIGS) solar cells
	12.4 Cu2ZnSn(S,Se)4 solar cells
	12.5 CdTe solar cells
	12.6 Sb2Se3 solar cells
	12.7 CsPb(I1-xBrx)3 solar cells
	12.8 Environmental and economic concerns
	12.9 Conclusion
	References
13. Efficient Metal Oxide-Based Flexible Perovskite Solar Cells
	13.1 Introduction
	13.2 Requirement for alternate energy resources
	13.3 Metal oxide nanostructures
	13.4 Metal oxide based flexible solar cells
	13.5 Metal oxides based flexible perovskite solar cells
	13.6 Recent advancement in metal oxide-based flexible perovskite solar cells
	13.7 Summary and outlook
	Acknowledgments
	References
14. Flexible Solar Cells Based on Chalcogenides
	14.1 Introduction
	14.2 Merits of flexible solar cells
	14.3 Progress and development on different substrates
		14.3.1 CIGS
			14.3.1.1 Polyimide
			14.3.1.2 Metal foils
			14.3.1.3 Ceramic and other materials
		14.3.2 CdTe
			14.3.2.1 Metal Foils
			14.3.2.2 Polymer
			14.3.2.3 Ceramics
		14.3.3 CZTS/CZTS(Se)
			14.3.3.1 Metal foils
			14.3.3.2 UTG
			14.3.3.3 Polymer and other materials
		14.3.4 Sb2Se3
	14.4 Fabrication issues and challenges with flexible solar cells
		14.4.1 Crack initiation
		14.4.2 Performance degradation under bending
		14.4.3 Substrate choice
		14.4.4 Electrodes issues
		14.4.5 Stability and scalability issues
	14.5 Future prospects and strategies for further advancements
		14.5.1 Absorber optimization
		14.5.2 New chalcogenide materials
		14.5.3 Optimizing every layer of solar module
		14.5.4 Material database and machine learning algorithms
		14.5.5 Rigorous testing
		14.5.6 Development of transparent/semitransparent solar cells
		14.5.7 Integration with existing technologies
	14.6 Conclusion
	References
15. Perovskite-Based Flexible Solar Cells
	15.1 Introduction
	15.2 Device structure and development of FPSCs
		15.2.1 Device structure of FPSC
		15.2.2 Development of FPSCs
	15.3 FPSC fabrication methods
		15.3.1 Laboratory scale fabrication methods
			15.3.1.1 Spin coating
			Advantages
			Disadvantages
			15.3.1.2 Thermal evaporation
			Advantages
			Disadvantages
		15.3.2 Large scale fabrication methods
			15.3.2.1 Inkjet printing
			Advantages
			Disadvantages
			15.3.2.2 Blade coating
			Advantages
			Disadvantages
			15.3.2.3 Spray coating
			Advantages
			Disadvantages
			15.3.2.4 Slot-die coating
			Advantages
			Disadvantages
	15.4 Materials for FPSCs
		15.4.1 Perovskite absorber layer
		15.4.2 Charge transport layers
			15.4.2.1 Electron transport layer
			15.4.2.2 Hole transport layer
		15.4.3 Flexible substrates
			15.4.3.1 Polymer (or plastic) substrates
			15.4.3.2 Metal substrates
			15.4.3.3 Fiber shaped PSCs
			15.4.3.4 Other flexible substrates
		15.4.4 Transparent conducting layer
		15.4.5 Encapsulation
	15.5 Recycling of FPSCs
	15.6 Challenges and future perspectives
		15.6.1 Environmental stability
		15.6.2 Mechanical stability
		15.6.3 High manufacturing cost
		15.6.4 Large-area fabrication
		15.6.5 Toxicity
	15.7 Applications of FPSCs
	15.8 Conclusion
	References
16. Quantum Dots Based Flexible Solar Cells
	16.1 Introduction
	16.2 Theoretical background of QDs
		16.2.1 Quantum size effect
		16.2.2 Multiple exciton generation
		16.2.3 Ultrafast charge transfer
	16.3 Synthesis and characterization of QDs
		16.3.1 Colloidal synthesis
		16.3.2 Surface engineering
	16.4 QDs based flexible heterojunction solar cell
	16.5 QD based flexible sensitized solar cells
	16.6 QDs based flexible perovskite solar cells
	16.7 Flexible QD-silicon hybrid solar cells
	16.7 Conclusion
	References
17. A Method of Strategic Evaluation for Perovskite-Based Flexible Solar Cells
	17.1 Introduction
	17.2 Perovskite-based solar cells' working mechanism
		17.2.1 The future of perovskite-based solar cells
	17.3 Methodology
		17.3.1 AHP analysis
	17.4 Conclusions
	References
18. Flexible Batteries Based on Li-Ion
	18.1 Introduction
	18.2 Flexible electrodes
		18.2.1 Flexible anodes
			18.2.1.1 Carbon materials
			18.2.1.2 Mxenes
		18.2.2 Flexible cathodes
	18.3 Flexible electrolytes
	18.4 Battery structures
	18.5 Fabrication of FLIBs
	18.6 Conclusion
	References
19. Flexible Na-Ion Batteries
	19.1 Introduction
	19.2 Flexible Na-ion batteries
		19.2.1 Configurations
		19.2.2 Electrolytes
		19.2.3 Electrode materials
		19.2.4 Separators
	19.3 Conclusion
	References
20. Flexible Batteries Based on K-ion
	20.1 Introduction
	20.2 Working principle
	20.3 Influence of electrolytes and solid electrolyte interphase in K-ion based batteries
		20.3.1 Thermodynamic understanding of electrolyte reduction
		20.3.2 Comparison of K-ion SEI and Li-/Na-ion SEI
		20.3.3 Effects of electrolyte selection on SEI
		20.3.4 Mechanical stability of SEI
	20.4 Anode materials for K-ion based flexible batteries
		20.4.1 Carbon materials
		20.4.2 Phosphorus compounds
		20.4.3 Titanium-based compounds
		20.4.4 Alloying-type compounds
		20.4.5 Organic compounds
	20.5 Cathode materials for K-ion based flexible batteries
		20.5.1 Hexacyanometallate
		20.5.2 Layered metal oxides
		20.5.3 Polyanionic compounds
		20.5.4 Organic materials
	20.6 Summary and future outlooks
	References
21. Flexible Batteries Based on Zn-Ion
	21.1 Introduction
	21.2 Zinc-ion batteries and mechanisms
	21.3 Flexible zinc-ion batteries
		21.3.1 Polymer electrolytes
			21.3.1.1 PEO and derivatives
			21.3.1.2 PVA and derivatives
			21.3.1.3 PAM and derivatives
		21.3.2 Functionalities
		21.3.3 Flexible device constructions (electrodes)
	21.4 Current challenges and perspectives
		21.4.1 Voltage issue
		21.4.2 Structural enhancement
		21.4.3 Multifunctionalities
	21.5 Conclusions
	Reference
22. Fabrication Techniques for Wearable Batteries
	22.1 Introduction
	22.2 Wearable batteries
	22.3 Electrode fabrication approaches
		22.3.1 Substrate-enabled techniques
			22.3.1.1 Chemical vapor deposition
			22.3.1.2 Hydrothermal deposition
			22.3.1.3 Electrochemical deposition
			22.3.1.4 Electrospinning and electrospraying
			22.3.1.5 Solution dip coating
			22.3.1.6 Spray painting
			22.3.1.7 Biscrolling
		22.3.2 Substrateless techniques
			22.3.2.1 Electrospinning
			22.3.2.2 Wet spinning
			22.3.2.3 Melt spinning
			22.3.2.4 3D extrusion printing
	22.4 Structures and approaches for unification of electrodes
		22.4.1 Winding
		22.4.2 Twisting
		22.4.3 Coaxial assembly
	22.5 Integration of fiber electrodes/batteries into textiles for wearable applications
		22.5.1 Weaving
		22.5.2 Knitting
	22.6 Conclusion
	References
23. Carbon-Based Advanced Flexible Supercapacitors
	23.1 Introduction
	23.2 Carbon-based materials for FSCs
		23.2.1 Graphene
		23.2.2 Carbon nanotubes
		23.2.3 Bio-based carbon
	23.3 Synthesis of carbon-based materials
	23.4 Mechanisms of energy storage in supercapacitors
		23.4.1 Electrochemical double-layer capacitors
		23.4.2 Pseudo-capacitors
		23.4.3 Hybrid capacitors
	23.5 Carbon-based flexible supercapacitors
		23.5.1 Graphene-based flexible supercapacitors
		23.5.2 CNT-based flexible supercapacitors
		23.5.3 Bio-based FSCs
	23.6 Conclusion
	References
24. 2D Materials for Flexible Supercapacitors
	24.1 Introduction
	24.2 Classification, methods, and merits
		24.2.1 Graphene and its carbonaceous analogs
		24.2.1 TMCs and TMDs
		24.2.3 MXenes
		24.2.4 2D MOFs
		24.2.5 Other 2D/layered materials
		24.2.5 Hybrid 2D nanostructures
		24.2.6 Configurations of FSCs
	24.3 Challenges and prospects
	References
25. Flexible Supercapacitors Based on Metal Oxides
	25.1 Introduction
	25.2 Key characteristics of flexible supercapacitors
	25.3 Equations of super-capacitance measurement
	25.4 Metal oxide based-flexible supercapacitors
		25.4.1 Drawbacks of MOs for supercapacitors
		25.4.2 How to overcome the drawbacks?
		25.4.3 Various electrolytes in supercapacitors
		25.4.4 Various metal oxides in supercapacitors
			25.4.4.1 Ruthenium oxide-based supercapacitors
			25.4.4.2 Manganese-oxide-based supercapacitors
			25.4.4.3 Other metal oxide-based supercapacitors
		25.4.4 Transparent supercapacitors
	25.5 Conclusions
	Acknowledgments
	References
26. Recent Advances in Transition Metal Chalcogenides for Flexible Supercapacitors
	26.1 Introduction
	26.2 Substrates for flexible supercapacitors
	26.3 Metal chalcogenides and their categories
		26.3.1 Unary-metal chalcogenides
		26.3.2 Binary or ternary metal chalcogenide
	26.4 How does the electrode system work?
	26.5 Recent developments in the metal chalcogenide-based Flexible Supercapacitors
	26.6 Conclusion
	Acknowledgment
	References
27. MOFs-Derived Metal Oxides-Based Compounds for Flexible Supercapacitors
	27.1 Introduction
	27.2 MOFs-derived metal oxides for flexible supercapacitors
		27.2.1 MOFs-derived binary metal oxides
			27.2.1.1 Co-oxides materials
			27.2.1.2 Fe-oxides materials
			27.2.1.3 Ce-oxides materials
		27.2.2 MOFs-derived ternary or TMMOs
			27.2.2.1 Porous ZnCo2O4 material
			27.2.2.2 MnCo2O4 materials
			27.2.2.3 NixCo3-xO4 material
		27.2.3 MOFs-derived metal oxide/composite
	27.3 Conclusions
	References
28. Textile-Based Flexible Supercapacitors
	28.1 Introduction
	28.2 Classification of supercapacitor based on storage mechanism
		28.2.1 Electrical double layer capacitors
		28.2.2 Pseudocapacitors
		28.2.3 Hybrid supercapacitors
	28.3 Components of supercapacitors
		28.3.1 Electrode
		28.3.2 Electrolyte
		28.3.3 Separator
		28.3.4 Current collector
	28.4 Textile-based supercapacitors
		28.4.1 Fiber-based supercapacitors
			28.4.1.1 Parallel fiber structure
			28.4.1.2 Twisted fiber structure
			28.4.1.3 Coaxial fiber structure
		28.4.2 Fabric supercapacitors
	28.5 Fiber-based electrodes
		28.5.1 Conventional fibers based fiber electrodes
		28.5.2 Metal yarns/wires/threads-based fiber electrodes
		28.5.3 Graphene yarn-based electrodes
		28.5.4 CNT yarn-based fiber electrodes
		28.5.5 Hybrid fiber-based supercapacitor electrodes
	28.6 Fabric-based electrodes for supercapacitors
		28.6.1 Metal mesh-based electrodes
		28.6.2 Carbon fabric-based electrodes
		28.6.3 Conventional fabric-based electrodes
	28.7 Applications
	28.8 Conclusion and future perspective
	Reference
29. Current Development and Challenges in Textile-Based Flexible Supercapacitors
	29.1 Introduction
	29.2 Classification and properties of textile fabrics
		29.2.1 Classification of textile fabrics
			29.2.1.1 Man-made fibers
			29.2.1.2 Natural fibers
		29.2.2 Properties of textile fibers for supercapacitor applications
	29.3 Textile based flexible supercapacitors (TFSCs)
	29.4 Design strategies for TFSCs application
	29.5 Conclusion and future perspective
	References
30. Flexible Supercapacitors Based on Nanocomposites
	30.1 Introduction
	30.2 Carbon nanomaterial-incorporated nanocomposites for FSCs
		30.2.1 Carbon nanomaterials
		30.2.2 Carbon-metal oxide nanocomposites
		30.2.3 Carbon-conducting polymer nanocomposites
		30.2.4 Carbon-mxene nanocomposites
	30.3 Device configurations of nanocomposite-based FSCs
		30.3.1 One-dimensional fiber-shaped FSCs
		30.3.2 Two-dimensional film-shaped FSCs
		30.3.3 Three-dimensional structural FSCs
	30.4 Practical applications of nanocomposite-based FSCs
		30.4.1 FSCs for wearable electronic devices
		30.4.2 FSCs for flexible electronic devices
	30.5 Summary and perspectives
	Acknowledgments
	References
31. Textile-Based Flexible Nanogenerators
	31.1 Introduction
	31.2 Piezoelectric nanogenerators
	31.3 Textile-based piezoelectric nanogenerators
	31.4 Pyroelectric and hybrid nanogenerators
	31.5 Triboelectric nanogenerators (TENG)
	31.6 Conclusion
	References
Index