G. V. Kamarchuk, K. I. Pokhodnya, and A. V. Khotkevich, Point-contact-spectroscopy study of oscillatory spectrum of the organic conductor b-(BEDT-TTF)₂I₃, Low Temp. Phys. 18, (1992) [Fiz. Nizk. Temp. 18, 523-525, (1992)].