Root Vegetables: New Uses for Old Crops—Wanda W. Collins
Andean Tuber Crops: Worldwide Potential—Calvin R. Sperling and Steven R. King
New Horticultural Crops in New Zealand—Errol W. Hewett
Neglected Crops: 1492 from a Different Perspective—J.E. Hernándo Bermejo and J. León (eds.)
Oca can be found in Lost Crops of the Incas from National Academy Press
Oca—Descriptores de Oca—Link to the publication on the International Plant Genetic Resources Institute web site