“…Only a few conditions on the parameters are known: if IOF(2n, λ) exists, then λ < 1 · 3 · ... · (2n − 3) [4]; each IOF(2n, λ) can be embedded in a simple IOF(2s, λ), provided that λ < 2n < s [16]. Six infinite classes of indecomposable one-factorizations have been constructed so far, namely a simple IOF(2n, n − 1) when 2n − 1 is a prime [16], IOF(2(λ + p), λ) where λ > 2 and p is the smallest prime wich does not divide λ [3] (an improvement of this result can be found in [15]), a simple IOF(2 h + 2, 2) where h is a positive integer [27], IOF(q 2 + 1, q − 1) where q is an odd prime number [26], a simple IOF(q 2 + 1, q + 1) for any odd prime power q [25], and a simple IOF(q 2 , q) for any even prime power q [25]. Most of these constructions arise from finite geometry.…”