Identification, Images, & Information
For Insects, Spiders & Their Kin
For the United States & Canada
This cite is a "catalogue of literature about all mayfly taxa. compiled by N.J. Kluge".

The reference section is a comprehensive bibliography of Ephemeroptera articles. A significant fraction are available for full text download.
http://www.insecta.bio.spbu.ru/z/Eph-spp/index.htm