What are non-fiction resources about butterflies?

The Audubon Society Handbook for Butterfly Watchers, The Butterfly Book, Caterpillars in the Field and Garden, A Field Guide to the Butterflies, and Garden Butterflies of North America are non-fiction resources about butterflies. The above-mentioned resources focus upon North American even though some lepidopterans, such as the monarch and the mourning cloak, will be familiar strays and vagrants to butterfly-watchers elsewhere. The National Audubon Society and the National Wildlife Federation maintain websites whose non-fiction resources include images and information on butterflies.