@article{ASNSP_1961_3_15_4_337_0,
     author = {Peetre, Jaak},
     title = {Mixed problems for higher order elliptic equations in two variables, {I}},
     journal = {Annali della Scuola Normale Superiore di Pisa - Scienze Fisiche e Matematiche},
     pages = {337--353},
     publisher = {Scuola normale superiore},
     volume = {Ser. 3, 15},
     number = {4},
     year = {1961},
     mrnumber = {140826},
     zbl = {0108.28802},
     language = {en},
     url = {http://www.numdam.org/item/ASNSP_1961_3_15_4_337_0/}
}