Khrapak, S. A., Morfill, G. E., Fortov, V. E., D'yachkov, L. G., Khrapak, A. G., & Petrov, O. F. (2007). Attraction of positively charged particles in highly collisional plasmas. Physical Review Letters, 99(5): 055003. doi:10.1103/PhysRevLett.99.055003.