P. Juutinen, G. Lu, J. Manfredi, B. Stroffolini:
"Convex functions on Carnot groups "
Revista Matematica Iberoamericana (Accepted Paper) 2005

T. Champion, L. De Pascale, P. Juutinen:
The $\infty$-Wasserstein distance: local solutions and existence of optimal transport maps
SIAM Journal of Mathematical Analysis Vol. 40, N. 1, p. 1-20, 2008