@article{
    KOTZ08,
    author = {Kaski, Petteri and {\"O}sterg{\aa}rd, Patric R. J. and Topalova, Svetlana and Zlatarski, Rosen},
    title = "Steiner triple systems of order 19 and 21 with subsystems of order 7",
    url = "http://www.tcs.hut.fi/~pkaski",
    journal = "Discrete Mathematics",
    number = "13",
    abstract = "Steiner triple systems (STSs) with subsystems of order 7 are classified. For order 19, this classification is complete, but for order 21 it is restricted to Wilson-type systems, which contain three subsystems of order 7 on disjoint point sets. The classified STSs of order 21 are tested for resolvability; none of them is doubly resolvable.",
    volume = "308",
    year = "2008",
    keywords = "classification, doubly resolvable design, Steiner triple system, subsystem",
    pages = "2732--2741"
}