From the mid-1950s to about the time Chomsky and Morris Halleˇ¦s The sound pattern of English appeared in 1968, which brings together the two principal lines of development. As a student originally of Zellig Harris, Chomskyˇ¦s background was in the rigorously formal, procedural, distributional sort of American structuralism. Halle, on the other hand, was a student of Roman Jakobson, trained in ˇ§European traditionˇ¨. Their collaboration resulted in a theory radically different from either source, but with Essential roots in both.