Philip Lake, Andrew J. Lamoureux, Edward B. Tylor, Walter Lehmann and James S. Mann, 1911 Encyclopædia Britannica (1911)
“ In a general sense these ranges may be considered part of the eastern branch of the Sierra Madre Occidental, which turns eastward on the 20th parallel and crosses the plateau in a south by east direction. Southward the plateau is traversed by many low ranges and breaks down in terraces, forming one of the most fertile and attractive parts of the republic. Close to the capital are the Sierra de Ajusco, whose highest point is 13,078 ft. ”
