Fülöp Ferenc;  Wamhoff Heinrich;  Sohár Pál: Imidazo[1’,2’:3,4]pyrimido[6,1-a]isoquinoline and Pyrimido[1’,2’:3,4]pyrimido[6,1-a]isoquinoline Ring Systems by Tandem Cyclization.
  SYNTHESIS-STUTTGART, 27 (7).  pp. 863-867.  ISSN 0039-7881 (1995)