1. On the structure of t-designs;Graham;SIAM J. Algebraic Discrete Methods,1980
2. The module structure of integral designs;Graver;J. Combin. Theory Ser. A,1973
3. Numerical analysis of designs;Hall;Congr. Numer.,1987
4. Halving the complete design;Hartman,1987
5. The theory of trade-off for t-designs;Hedayat,1990