Banday, A. J. Cosmology, MPI for Astrophysics, Max Planck Society;
Eriksen, H. K., Lilje, P. B., Banday, A. J., & Górski, M. (2004). Estimating N-Point Correlation Functions from Pixelized Sky Maps. Astrophysical Journal Supplement Series, 151(1), 1-11. doi:10.1086/381740.