Not only Elvis' back-up singers, also for Jim Reeves and Marty Robbins (author).
Dennis Lotis [Brit on Pye]
Marty Robbins [reissued on cd Honky Tonk Rockabillies Vol 1 (Cotton Town Jubilee)]
Rusty York [regional hit in Cincinnati (Note label), distributed nationally by Chess]
Chaussettes Noires [as Chérie oh chérie]
Pingouins [as Oh les filles]
Au Bonheur Des Dames [idem]
Very likely from the source that inspired swamp pop classic Sugar Bee (see there).