The Resource Handbook of Electronics
Jerry C. Whitaker
Electronics Handbook (1)
RF Components and Circuits
Joseph J. Carr
German Wikibook
Various
Robotics Demystified
Edwin Wise
Demystified (1)
Colloquial German
Dietlinde Hatherall & Glyn Hatherall
Colloquial Series (1)
Colloquial German 2: The Next Step in Language Learning
Annette Duensing
Colloquial Series (2)