Hymenoptera of America north of Mexico : synoptic catalog - Krombein, Karl V. (U.S. Dept. of Agriculture, 1951)

Hymenoptera of America north of Mexico : synoptic catalog, first supplement - Krombein, Karl V. (U.S. Dept. of Agriculture, 1958)

Hymenoptera of America north of Mexico : synoptic catalog, second supplement - Krombein, Karl V. (U.S. Dept. of Agriculture, 1967)