Appel, Charles A. <br/><br/>
Summary of selected computer programs produced by the U.S. Geological Survey for simulation of ground-water flow and quality, 1994 / 
by Charles A. Appel and Thomas E. Reilly 
 - Washington :  U.S. Government Printing Office,  1994 
 - 98 p. :  27 cm. 
 - U.S. Geological Survey circular ;  1104 .