We investigate linear combinations of characters for minimal Virasoro models
which are representable as a products of several basic blocks. Our analysis is
based on consideration of asymptotic behaviour of the characters in the
quasi-classical limit. In particular, we introduce a notion of the secondary
effective central charge. We find all possible cases for which factorization
occurs on the base of the Gauss-Jacobi or the Watson identities. Exploiting
these results, we establish various types of identities between different
characters. In particular, we present several identities generalizing the
Rogers-Ramanujan identities. Applications to quasi-particle representations,
modular invariant partition functions, super-conformal theories and conformal
models with boundaries are briefly discussed.Comment: 25 pages (LaTex), minor corrections, one reference adde