  Perturbative subcritical series expansions for the steady properties of a
class of one-dimensional nonequilibrium models characterized by
multiple-reaction rules are presented here. We developed long series expansions
for three nonequilibrium models: the pair-creation contact process, the
A-pair-creation contact process, which is closely related system to the
previous model, and the triplet-creation contact process. The long series
allowed us to obtain accurate estimates for the critical point and critical
exponents. Numerical simulations are also performed and compared with the
series expansions results.
