@article{ASNSP_1974_4_1_1-2_1_0,
     author = {Grubb, Gerd},
     title = {Properties of normal boundary problems for elliptic even-order systems},
     journal = {Annali della Scuola Normale Superiore di Pisa - Classe di Scienze},
     pages = {1--61},
     publisher = {Scuola normale superiore},
     volume = {Ser. 4, 1},
     number = {1-2},
     year = {1974},
     mrnumber = {492833},
     zbl = {0309.35034},
     language = {en},
     url = {http://www.numdam.org/item/ASNSP_1974_4_1_1-2_1_0/}
}