[A] Amir D.: 
On Jung's constant and related constants in normed linear spaces. Pacific J. Math. 118 (1985), 1-15. 
MR 0783011 | 
Zbl 0529.46011 
[B] Beauzamy B.: 
Introduction to Banach Spaces and Their Geometry. North-Holland, Amsterdam, 1982. 
MR 0670943 | 
Zbl 0491.46014 
[B-S] Bernal J., Sullivan F.: 
Multi-dimensional volumes, super-reflexivity and normal structure in Banach spaces. Illinois J. Math. 27 (1983), 501-513. 
MR 0698311 | 
Zbl 0512.46013 
[G-S] Geremia R., Sullivan F.: 
Multi-dimensional volumes and moduli of convexity in Banach spaces. Ann. Mat. Pura Appl. (4) 127 (1981), 231-251. 
MR 0633401 | 
Zbl 0472.46018 
[Si] Silverman E.: 
Definition of area for surfaces in metric spaces. Riv. Mat. Univ. Parma (4) 2 (1951), 47-76. 
MR 0042503 
[Su] Sullivan F.: 
A generalization of uniformly rotund Banach spaces. Canad. J. Math 31 (1979), 628-636. 
MR 0536368 | 
Zbl 0422.46011 
[Y-W] Yu Xin-Tai, Wang Jia-Ping: On k-rotund moduli and k-tonvex moduli (Chinese). J. East China Normal UNiv. 1 (1981), 1-8.