(1)
Qin, X.-Y.; Jin, T.-S.; Zhou, Z.-X.; Li, T.-S. Silica Sulfuric Acid: An Efficient and Versatile Catalyst for One-Pot Synthesis of Substituted 5-Oxo-1,4,5,6,7,8-Hexahydroquinoline Derivatives. ajc 2010, 22, 1179-1182.