@incollection{Grohmann2013,
  author    = {Kleanthes K. Grohmann},
  title     = {"Natural relations" : a note on X'-structure},
  booktitle = {Zentrum f{\"u}r Allgemeine Sprachwissenschaft, Sprachtypologie und Universalienforschung, Berlin, 2001; ZAS papers in linguistics Vol. 21},
  volume    = {21},
  url       = {http://www.zas.gwz-berlin.de/fileadmin/material/ZASPiL_Volltexte/zp21/zaspil21-grohmann.pdf},
  year      = {2013},
}