This document summarizes several key studies on third language acquisition of syntax from the early 1990s to 2009. It describes studies that found evidence of transfer from a non-native language (L2 English) influencing the acquisition of verb placement in L3 German. Subsequent studies investigated whether multilingual grammars are more or less conservative than monolingual grammars and found multilinguals follow a less restrictive learning process. Later studies examined features like complementizers, determiners, and tense/agreement and whether transfer occurs from L1 or L2 backgrounds.