Two-Higgs-doublet models and the Yukawa process at LEP1

We investigate the production of Higgs bosons $A/h$ via the Yukawa process $Z\ra f\bar{f} \ra f\bar{f} A/h$ taking into account QCD corrections and fermion mass effects. We estimate the discovery reach of this process and/or bounds on the parameter space of two-Higgs doublet models which can be derived from the analysis of $b {\bar b} \tau^+ \tau^-$ events at LEP1. These limits have important consequences for extended models of electroweak interactions and their experimental verification/improvement are welcome.