@article{CM_1972__25_1_71_0, author = {Helfenstein, H. G. and Katz, E.}, title = {Intermediate flexibility of surfaces}, journal = {Compositio Mathematica}, pages = {71--78}, publisher = {Wolters-Noordhoff Publishing}, volume = {25}, number = {1}, year = {1972}, mrnumber = {320962}, zbl = {0237.53047}, language = {en}, url = {http://www.numdam.org/item/CM_1972__25_1_71_0/} }
Helfenstein, H. G.; Katz, E. Intermediate flexibility of surfaces. Compositio Mathematica, Tome 25 (1972) no. 1, pp. 71-78. http://www.numdam.org/item/CM_1972__25_1_71_0/
Flächenverbiegung im Grossen, Berlin 1957.
[1]The mathematical theory of rigid surfaces, Lecture notes, University of North Carolina, 1954.
[2]