sentences:  His 1999 book for general readers, "Nihongo Renshūchō" (, Japanese Exercise Book), sold 1.8 million copies.Ōno made a significant contribution to the field of Japanese quantitative linguistics by indicating a statistical relationship, known as "Ōno's lexical law", between the category of classical Japanese literary works and the rate of usage of word classes in their lexicons.Over the last three decades, Ōno has won notability, though not always complimentary, for his support of the hypothesis, first put forward by Susumu Shiba in 1970, and developed by Akira Fujiwara, most notably in 1981, that the Japanese and the Tamil languages share a common ancestry.