  The space of local operators in massive deformations of conformal field
theories is analysed. For several model systems it is shown that one can define
chiral sectors in the theory, such that the chiral field content is in a
one-to-one correspondence with that of the underlying conformal field theory.
The full space of operators consists of the descendent spaces of all scalar
fields. If the theory contains asymptotic states which satisfy generalised
statistics, the form factor equations admit in addition also solutions
corresponding to the descendent spaces of the para-fermionic operators of the
same spin as the asymptotic states. The derivation of these results uses
$q$-sum expressions for the characters and $q$-difference equations used in
proving Rogers-Ramanujan type identities.
