EN
Let B be a set of complex numbers of size n. We prove that the length of the longest arithmetic progression contained in the product set B.B = {bb' | b,b' ∈ B} cannot be greater than O((nlog²n)/(loglogn)) and present an example of a product set containing an arithmetic progression of length Ω(nlogn). For sets of complex numbers we obtain the upper bound $O(n^{3/2})$.