Some remarks on barycentric-sum problems over cyclic groups
  We derive some new results on the k-th barycentric Olson constants of abelian groups (mainly cyclic). This quantity, for a finite abelian (additive) group (G,+), is defined as the smallest integer l such that each subset A of G with at least l elements contains a subset with k elements {g_1, ..., g_k} satisfying g_1 + ... + g_k = k g_j for some 1 <= j <= k. 
Oscar Ordaz, Alain Plagne (CMLS-EcolePolytechnique), Wolfgang A.   Schmid (LAGA)
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