Lanzerotti, L., Maclennan, C., & Schulz, M. (1970). Radial Diffusion of Outer-Zone Electrons: An Empirical Approach to Third-Invariant Violation. Journal Of Geophysical Research, 75, 5351-5371. http://doi.org/10.1029/JA075i028p05351 (Original work published October 1970)
Schulz, M., & Eviatar, A. (1969). Diffusion of Equatorial Particles in the Outer Radiation Zone. Journal Of Geophysical Research, 74, 2182-2192. http://doi.org/10.1029/JA074i009p02182 (Original work published May 1969)