Enumeration of the doubles of the projective plane of order 4. - Veerle Fack; Svetlana Topalova; Joost Winne; Rosen Zlatarski (Discret. Math., 2006)

Steiner triple systems of order 19 and 21 with subsystems of order 7. - Petteri Kaski; Patric R. J. Östergård; Svetlana Topalova; Rosen Zlatarski (Discret. Math., 2008)