Trainable Grammars for Speech Recognition. James K. Baker.
Speech Communication Papers for ASA'97. 1979. 547-550.

Inside-Outside Estimation of a Lexicalized PCFG for German.
Franz Beil and Glenn Carroll and Detl

A context-free grammar augmented with non-negative weights for all grammar rules resulting in a probability distribution for both the syntax trees and the language of the grammar. Probabilistic context-free grammars may be used (i) to disambiguate the analyses of a given sentence, and (ii) in language modeling.