Just looking through book I picked up at library last week:
Strength and Power in Sport edited by Komi, Vol. III of Encyclopaedia of Sports Medicine, IOC Medical Commission Publication, 1991.
Chp. 14 is "Use of electrical stimulation in strength and power training" by Dudley and Harris. Have just glanced through that chapter but does basically a review of various articles and is littered with citations at end of the chapter which may provide you with more info.
they do have several it looks like that support ems strength gains, Delitto is one.
email if you like and if tiger land does not have, i can break the law and snail mail chapter to you.