@article{Halliday61,
  author	= {Halliday, Michael A. K.},
  year		= {1961},
  title		= {Categories of the theory of grammar},
  journal	= {Word},
  volume	= {17},
  number	= {3},
  pages		= {241--292},
  note		= {Reprinted in abbreviated form in Halliday (1976) edited by Gunther R. Kress, pp 52-72}
}