Music Arab - Avicenna - Disjoint and Equal
Avicenna Binary Rhythm page 2
Avicenna (Ibn Sina 980 - 1037) and his Kitab S. Sifa on measure (Persian), translated into French by Baron Rodolphe D’Erlanger, published in 1935 (and known to Bartok before then) on movement/disruption in rhythm (page 185 -):
Music Arab - Avicenna