@incollection{Nwogu91,
  author	= {Nwogu, Kevin and Bloor, Thomas},
  editor	= {Ventola, Eija},
  year		= {1991},
  title		= {Thematic progression in professional and popular medical texts},
  booktitle	= {Functional and systemic linguistics: approaches and uses},
  publisher	= {Mouton de Gruyter},
  address	= {Berlin}
}