Post-common-envelope binaries from SDSS - IX: Constraining the common-envelope efficiencyM. Zorotovic, M. R. Schreiber, B. T. Gänsicke and A. Nebot Gómez-MoránA&A, 520 (2010) A86DOI: https://doi.org/10.1051/0004-6361/200913658