C. Cusack, “Petsche, Johanna J. M. 2015. Gurdjieff and Music: The Gurdjieff/de Hartmann Piano Music and its Esoteric Significance. Leiden and Boston, MA: Brill. xvi + 279pp. Ebook. US$130. E-ISBN: 9789004284449. Hbk. US$142.00. ISBN-13: 96789004284425”, FIRN, vol. 11, no. 1, pp. 121–122, Nov. 2016, doi: 10.1558/firn.32188.