The borderline between the compound and the complex sentence is very vague and the difference between them can be neutralized. It occurs when a sub-clause comes to be very loose, losing its grammatical tension. Neutralization between subordination and coordination is observed when 1. a temporal clause (a while-clause, or a when-clause) expresses contrast rather than time {His sense of property is extreme, while you have practically none (J.Galsworthy); He wears fine clothes while I go in rags (O.Wilde)}. 2. Neutralization occurs in structures with continuative attributive clauses {The casino had been dropping money lately which shouldn’t be (M. Puso. Godfather)}→ The casino had been dropping money lately and that shouldn’t be }.The conjunctive pronoun which is easily replaced here by the phrase and that.. 3. Neutralization occurs when a when-clause expresses a successive action {I was listening, and thinking how the wind assailed and tore it when I heard a footstep on the stairs .Ch. Dickens. Great Expectations)→ and then I heard a footstep on the stairs}.