There are 270,474,142 nonisomorphic 2-(9,4,6) designs

Reference:

Patric R.J. Östergård. There are 270,474,142 nonisomorphic 2-(9,4,6) designs. Journal of Combinatorial Mathematics and Combinatorial Computing, 37(1):173–176, 2001.

Suggested BibTeX entry:

@article{PO:there,
    author = {Patric R.J. \"Osterg\aard},
    journal = {Journal of Combinatorial Mathematics and Combinatorial Computing},
    number = {1},
    pages = {173--176},
    title = {There are 270,474,142 nonisomorphic 2-(9,4,6) designs},
    volume = {37},
    year = {2001},
}