Facile and Convenient Synthetic Methods for Fluorine-Containing Benzo[c]thioxanthenes and Benzo[c]xanthenes from N,N-Dimethyl-1-naphthylamine - Okada, Etsuji; Masuda, Ryoichi; Hojo, Masaru; Imazaki, Naonori; Takahashi, Koichi (Synthesis, 1992)