@inbook {IOPORT.05934378,
    author       = {B\'echet, Denis and Dikovsky, Alexandre and Foret, Annie},
    title        = {Categorial grammars with iterated types form a strict hierarchy of $k$-valued languages.},
    year         = {2011},
    booktitle    = {Implementation and application of automata. 16th international conference, CIAA 2011, Blois, France, July 13--16, 2011. Proceedings},
    isbn         = {978-3-642-22255-9},
    pages        = {42-52},
    publisher    = {Berlin: Springer},
    doi          = {10.1007/978-3-642-22256-6_5},
    abstract     = {Summary: The notion of $k$-valued categorial grammars where a word is associated to at most $k$ types is often used in the field of lexicalized grammars as a fruitful constraint for obtaining several properties like the existence of learning algorithms. This principle is relevant only when the classes of $k$-valued grammars correspond to a real hierarchy of languages. Such a property had been shown earlier for classical categorial grammars. This paper establishes the relevance of this notion when categorial grammars are enriched with iterated types.},
    identifier   = {05934378},
}