A (real or complex) Banach space E is said to have the unconditionaly property for martingale differences (UMD-property, for short) if E-values martingale differences are unconditional in Lp(E;[0,1]). The main reason for the interest in this new class of spaces is that the analogues of several classical results on martingales and singular integrals are also true for a Banach space belonging to this class.
@article{urn:eudml:doc:38160, title = {Interpolation with function parameter and UMD spaces.}, journal = {Extracta Mathematicae}, volume = {1}, year = {1986}, pages = {22-24}, language = {en}, url = {http://dml.mathdoc.fr/item/urn:eudml:doc:38160} }
Cobos Díaz, Fernando. Interpolation with function parameter and UMD spaces.. Extracta Mathematicae, Tome 1 (1986) pp. 22-24. http://gdmltest.u-ga.fr/item/urn:eudml:doc:38160/