Itay Ben-Yaacov Anand Pillay Evgueni Vassiliev Lovely pairs of models. 235-261 2003 122 Ann. Pure Appl. Logic 1-3 http://dx.doi.org/10.1016/S0168-0072(03)00018-6 db/journals/apal/apal122.html#Ben-YaacovPV03