Interlanguage Signs and Lexical Transfer Errors
  A theory of interlanguage (IL) lexicons is outlined, with emphasis on IL lexical entries, based on the HPSG notion of lexical sign. This theory accounts for idiosyncratic or lexical transfer of syntactic subcategorisation and idioms from the first language to the IL. It also accounts for developmental stages in IL lexical grammar, and grammatical variation in the use of the same lexical item. The theory offers a tool for robust parsing of lexical transfer errors and diagnosis of such errors. 
Atle Ro (Department of Phonetics and Linguistics, University of   Bergen)