@article{GAU_1979-1981__7-8__A11_0,
     author = {Dwork, Bernard M.},
     title = {On Apery's differential operator},
     journal = {Groupe de travail d'analyse ultram\'etrique},
     publisher = {Secr\'etariat math\'ematique},
     volume = {7-8},
     year = {1979-1981},
     note = {talk:25},
     zbl = {0493.12031},
     language = {en},
     url = {http://www.numdam.org/item/GAU_1979-1981__7-8__A11_0}
}

Dwork, Bernard. On Apery's differential operator. Groupe de travail d'analyse ultramétrique, Volume 7-8 (1979-1981) , Talk no. 25, 6 p. http://www.numdam.org/item/GAU_1979-1981__7-8__A11_0/