Re: Sihah Sittah
Only first two books have included the sahih traditions (what the authors thought were sahih), the last 4 books contain both sahih and daeef traditions, but the authors have given their opion of what they think of the tradition. Hence if anyone qoutes from Tirmidhi, it does not mean that Imam tirmidhi considered it sahih, he may have written that he beleives its daeef.