Virkki, Niilo, et al. “HOWARDULA SP., A NEMATODE NEW FOR PUERTO RICO, PARASITIZING A PARTHENOGENETIC SWEET POTATO-ASSOCIATED FLEA BEETLE, CHAETOCNEMA PERPLEXA BLAKE”. The Journal of Agriculture of the University of Puerto Rico, vol. 73, no. 2, Apr. 1989, pp. 171-4, doi:10.46429/jaupr.v73i2.6421.