There are thousands of scientific publications that mention DEET. The most comprehensive that appear in peer-reviewed publications include:
Comparative Efficacy of Insect Repellents Against Mosquito Bites. New England Journal of Medicine 2002:347: 13-18
http://content.nejm.org/cgi/content/full/347/1/13
Repelling Mosquitoes—Perspective, New England Journal of Medicine 2002:347: 13-18
http://content.nejm.org/cgi/content/full/347/1/2
Insect Repellents, Principles, Methods, and Uses. Debboun, M; Frances, SP; Strickman, D. editors. CRC Press, 2007