... is not contained in a coset of a proper subgroup of Hn, hence it is a basis for some order h bounded by a function depending only on p: indeed by a theorem of Freiman in arbitrary finite groups (see =-=[T]-=-, paragraph 4.9), it is known that if A is not included in some coset of some proper subgroup of Hn then |A · A| ≥ 3|A|/2. From this we deduce by iteration that the 2j-fold product set A2 j satisfies ...