APA
Watkins Jr, J. E., Cardel{\'u}s, C., Colwell, R. K., & Moran, R. C. (2006). Species richness and distribution of ferns along an elevational gradient in Costa Rica. American Journal of Botany, 93, 73–83.
Chicago/Turabian
Watkins Jr, James E, Catherine Cardel{\'u}s, Robert K Colwell, and Robbin C Moran. “Species Richness and Distribution of Ferns along an Elevational Gradient in Costa Rica.” American Journal of Botany 93 (2006): 73–83.
MLA
Watkins Jr, James E., et al. “Species Richness and Distribution of Ferns along an Elevational Gradient in Costa Rica.” American Journal of Botany, vol. 93, Botanical Society of America, 2006, pp. 73–83.