Hakim, G. J., and A. Canavan, 2005: Observed cyclone--anticyclone tropopause vortex asymmetries. J. Atmos. Sci., 62, 231--240. (pdf)
Hakim, G. J., C. Snyder, and D. J. Muraki, 2002: A new surface model for cyclone--anticyclone asymmetry. J. Atmos. Sci., 59, 2405--2420. (pdf)