McKenna-Lawlor, S. M. P., Afonin, V. V., Gringauz, K. I., Keppler, E., Kirsch, E., Richter, A. K., Witte, M., O'Sullivan, D., Thompson, A., Kecskemety, K., Somogyi, A. J., Szabo, L., & Varga, A. (1991). Interplanetary variability recorded by the SLED instrument aboard the PHOBOS spacecraft during that period of solar cycle 22 characterized by a transition from solar minimum - to solar maximum dominated conditions. Planetary and Space Science, 39, 47-56.