[16] In connection with Béla Bartók's music, this 0–5/6, 11 vertical span was identified as "cell z" by Leo Treitler in his "Harmonic Procedure in the Fourth Quartet of Béla Bartók," Journal of Music Theory 3, 2 (1959): 292–98. Treitler's designation came in partial response to an earlier study by George Perle, where two other "cells" were labeled "x" and "y"; see George Perle, "Symmetrical Formations in the StringQuartets of Béla Bartók," Music Review 16 (1955): 300–312. The role of "cell z" in Bartók's music generally—its relationship to other symmetrical cells, interval cycles, and various octatonic and diatonic orderings—is discussed at length in Elliott Antokoletz, The Music of Béla Bartók (Berkeley: University of California Press, 1984), pp. 67–137.