Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
credentials [krɪˈdɛnʃlz] npl (references) квалифика́ция fsg, достиже́ния ntpl (identity papers) рекоменда́ция, рекоменда́тельное письмо́
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.
Русский: