W. P.  Stephen, ?Solitary bees in North American agriculture: a perspective?, in For non-native crops, whence pollinators of the future?, K.  Strickler and Cane, J. H., Eds. Lanham, Maryland: Entomol. Soc. Amer., 2003, pp. 41 - 66.

K.  Strickler and Cane, J. H., For non-native crops, whence pollinators of the future?. Lanham, Maryland: Entomol. Soc. Amer., 2003, p. - 204.