Laser phase fluctuations in a four-level atomic system in N-configuration N. Singh, R. D’Souza, Q.V. Lawande and B.N. Jagatap Eur. Phys. J. D, 67 6 (2013) 110 Published online: 04 June 2013 DOI: 10.1140/epjd/e2013-40006-9