Facile Synthesis of Carboxylic Anhydrides Using 4,5-Dichloro-2-[(4-nitrophenyl)sulfonyl]pyridazin-3(2H)-one - Kim, Jeum-Jong; Park, Yong-Dae; Lee, Woo Song; Cho, Su-Dong; Yoon, Yong-Jin (Synthesis, 2003)