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IT References 
Apache Desktop Reference (R. Engelschall) Edmund's Computer Reference Guides
Dictionary of Programming Languages Networking Encyclopedia
Design Patterns Dictionary (in C++ and Java) [in C#] Programming Quick Reference Cards [Another]
HTML Encyclopaedia The Electronic Commerce Dictionary
Protocol Directory Encyclopedia of Graphics File Formats
Network Protocols Dictionary, Directory, Reference & Guide Searchable IT Encyclopedia (Webopedia)
Unified Modeling Language (UML) Dictionary [Another]  
Computer Programming Algorithms Directory Dictionary of Algorithms and Data Structures
Linux Dictionary [Mirror] [PDF] Technical Encyclopedia [Another]
Free Online Dictionary of Computing [Mirror] 3D Computer Dictionary