Appendix : “Picard groups of Zariski surfaces”
Compositio Mathematica, Volume 54 (1985) no. 1, p. 37-40
@article{CM_1985__54_1_37_0,
     author = {Blass, Piotr and Lang, Jeffrey},
     title = {Appendix : ``Picard groups of Zariski surfaces''},
     journal = {Compositio Mathematica},
     publisher = {Martinus Nijhoff Publishers},
     volume = {54},
     number = {1},
     year = {1985},
     pages = {37-40},
     zbl = {0624.14022},
     mrnumber = {782383},
     language = {en},
     url = {http://www.numdam.org/item/CM_1985__54_1_37_0}
}
Blass, Piotr; Lang, Jeffrey. Appendix : “Picard groups of Zariski surfaces”. Compositio Mathematica, Volume 54 (1985) no. 1, pp. 37-40. http://www.numdam.org/item/CM_1985__54_1_37_0/

[1] P. Blass: Picard groups of Zariski surfaces I. Comp. Math. 54 (1985) 3-36. | Numdam | MR 782383 | Zbl 0624.14021

[2] P. Blass: Groupes de Picard des surfaces de Zariski. Comptes Rendus des Seances de I'Academie des Sciences, I-315, 19 septembre 1983. | MR 734573

[3] Jeffrey Lang: The divisor class group of the surface zpn = G(x,y) over fields of characteristic p > 0. Journal of Algebra (2) 1983. | Zbl 0528.14017