D.  Castillo-Fernandez and Lambshead, P. J. D., ?Revision of the genus \emph{Elzalia} {Gerlach}, 1957 ({Nematoda: Xyalidae}) including three new species from an oil producing zone in the {Gulf of Mexico}, with a discussion of the sibling species problem?, Bulletin of the British Museum of Natural History, vol. 56, pp. 63?71, 1990.