An improved ephemeris and physical elements of ER Vul P. Harmanec, H. Božić, K. Thanjavur, R. M. Robb, D. Ruždjak and D. Sudar A&A, 415 1 (2004) 289-297 Published online: 03 February 2004 DOI: 10.1051/0004-6361:20034614