Richards, O.W., 1977
Hymenoptera: Introduction and Keys to Families (ed 2)
Overview of anatomy and explanation of terms used in the RES hymenoptera handbooks followed by the dichotomous key to families.
The second edition is not very different to the first, and the only obvious difference is that many of the illustrations in the text have been printed larger. On closer inspection, the names of a few of the parts of wasps have been changed.
Can be downloaded from the Royal Entomological Society website.