Given three Sobolev-Slobodeckii spaces with interpolating parameters, we study the embedding of one of them in the sum of the other two. We focus on the pathological case when the embedding does not hold. In this case, we indicate the construction of counterexamples. We also show the connection of our results with the Gagliardo-Nirenberg non-inequalities and the so called "sum-intersection property". Meeting Id: 977 8654 0401 Password: 268545