Hall, S.A. (2010) Early maize pollen from Chaco Canyon, New Mexico, USA. Palynology 34, 125-137. DOI: 10.1080/01916121003675746
Janzen, D.H. (1967) Why mountain passes are higher in the tropics. The American Naturalist 101, 233-249. DOI: 10.1086/282487
Tovar, C., Arnillas, C.A., Cuesta, F. & Buytaert, W. (2013) Diverging responses of tropical Andean biomes under future climate conditions. PLoS ONE 8, e63634. DOI: 10.1371/journal.pone.0063634