P. Astone, Ning Hua Zhu, E. Coccia et al.|Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fields|1999
Evan Mauceli, M. Visco, Zhiyong Geng et al.|Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fields|1997