The most notorious part of the standard is actually a misnomer. The panel is called "19-inch," but the actual mounting hole spacing is not 19 inches.
If you don't need the legal document but just the engineering data: eia310d standard pdf
Bookmark the official ANSI store page for "ANSI/EIA-310-D-1992" (or the current revision). For immediate reference, download a free, reputable dimensional summary from a major rack vendor. Your infrastructure will thank you. The most notorious part of the standard is