 Later in 1972 Hamblin independently rediscovered a form of duration calculus (interval logic), without being aware of the 1947 work of A. G. Walker on this topic, who was not interested in the tense aspect.Hamblin's duration calculus is very similar to that later developed by James Allen and Patrick J. Hayes in the mid 1980s.Hamblin was familiar with ancient Greek and several Asian and Pacific languages and in 1984 published a polyglot phrasebook on 25 of the latter, including "Burmese, Korean, Japanese, Fijian and Tahitian".