S. L.  Buchmann and Cane, J. H., ?Bees assess pollen returns while sonicating Solanum flowers?, Oecologia (Berlin), vol. 81, pp. 289 - 294, 1989.

T. E.  Shelly, Villalobos, E. M., Buchmann, S. L., and Cane, J. H., ?Temporal patterns of floral visitation for two bees foraging at Solanum?, Journal of the Kansas Entomological Society, vol. 66, pp. 319 - 327, 1993.