https://archive.org/download/GEM_Programmers_Guide_Volume_1_VDI_Apr85
GEM_Programmers_Guide_Volume_1_VDI_Apr85 directory listing
gem programmersguidevolumevdidirectory
https://archive.org/stream/GEM_Programmers_Guide_Volume_1_VDI_Apr85/GEM_Programmers_Guide_Volume_1_VDI_Apr85_djvu.txt
Full text of "GEM Programmers Guide Volume 1 VDI Apr85"
full textgem programmersguidevolumevdi