Shear horizontal BG surface acoustic waves on piezoelectrics: a historical note

In December of 1968 Jeffrey Bleustein of Yale University published an article predicting the existence of a new type of transverse surface acoustic wave (SAW) that could propagate on the surface of a piezoelectric crystal. This was followed within 20 days by the publication of an article by Yuri Gulyaev in January of 1969 predicting the same basic surface wave propagation. The wave took on the name Bleustein-Gulyaev or BG-wave, joining the names of Rayleigh, Love, Sezawa, and Stonely for distinct types of SAW. But is there more to the story than this? Were there works preceding those of Bleustein and Gulyaev which signaled an interest in exploring a new surface wave mode on piezoelectrics? What about the work of Shimizu, Nakamura, and Ohta, who in April of 1969 published both theoretical and experimental verification of the existence of such a wave independent of the knowledge of the Bleustein and Gulyaev papers? This paper explores the early roots and characteristics of the shear horizontal surface wave on a piezoelectric.