Ping, C.L., G.J. Michaelson, C.A. Stiles, and G. González. 2013. “Soil Characteristics, Carbon Stores, And Nutrients Distribution In Eight Forest Types Along An Elevation Gradient, Eastern Puerto Rico”. In Ecological Bulletins, Ecological Bulletins, Oxford: Wiley-Blackwell, 67-86. http://data.fs.usda.gov/research/pubs/iitf/BC_EB54-10_Ping_et_al.pdf.