Possibility of representation of a value of convexification of functio
n at the given point as a convex combination of the values of function
(spannability) is studied. Spannability of functions turned out to be
important in different fields e.g. in the study of quasi-cores of mon
etary economies with nonconvex preferences (mathematical economics), i
n the theory of relaxation of variation problems (variational calculus
). Apparently, Shapley and Shubik (Econometrica, 1966, 34, 805-827) we
re first to discuss it.