How was hijab (head covering) been made obligatory?

This question has ever been asked but i'm asking it again because: 1. The answers given are not concrete 2. Closed (as primarily opinion based) 3. Closed (as too broad) The questions are as follows: **First** is there any unambiguous source from Quran and/or Hadith which clearly mentions that Woman should cover their hair ? **Second**, Now if it is not clear, what are the main sources (e.g. Quran Verse or Hadiths) that were interpreted, if possible for the different madhabs ? **Third**, how the interpretations has lead to conclusion that Hijab is obligatory, clearly, the interpretations has been performed by different madhabs and in each madhabs, there was a logical entailment from the sources that Hijab is obligatory, in short what was the usool used for deriving this obligation, if possible for each madhabs ? NB: In no way, I am contesting the principle of Hijab, I am instead pro this practice, and sure that the great mujtahids have put forward such a practice as fard/wajib, then it must be important, i'm only wishing to see the evidence behind or the way they derived the ruling Jazak Allah