NES Four Score (Four Player Adapter) by Fredrik Olsson

NES Header Information by VmprHntrD

NES Schematics ( 1 - 2 - 3 - 4 - 5) Thanks to Rimma_69 and the NES Modifications Yahoo Group.

NES Zapper and Zapper Games FAQ by Spoondog

Nintendo Entertainment System Architecture by Marat Fayzullin

Nintendo FAQ Version .8 by Outkast

Power Pad Information by Tennessee Carmel-Veilleux

The Nintendo Entertainment System (NES) FAQ v3.0A by Martin Nielson