  We construct a monomorphism of the De Rham complex of scalar multivalued
meromorphic forms on the projective line, holomorphic on the complement to a
finite set of points, to the chain complex of the Lie algebra of $sl_2$-valued
algebraic functions on the same complement with coefficients in a tensor
product of contragradient Verma modules over the affine Lie algebra
$\hat{sl}_2$. We show that the existence of singular vectors in the Verma
modules (the Malikov-Feigin-Fuchs singular vectors) is reflected in the new
relations between the cohomology classes of logarithmic differential forms.
