We survey the status of minimal coverings of pairs with block sizes two, three, and four when \(\lambda = 1\), that is, all pairs from a \(v\)-set are covered exactly once. Then we provide a complete solution for the case \(\lambda = 2\).
Citation
M.J. Grannell, T.S. Griggs, R.G. Stanton. Minimal Perfect Bicoverings of \(K_v\) with Block Sizes Two, Three and Four[J], Ars Combinatoria, Volume 071. 125-138. .