Can I make a citation only in the beginning of a chapter? I asked a question related to my current thesis on mathoverflow.com and got there a really helpful answer by Iosif Pinelis. Obviously I want to cite his answer. Is it enough to put something like the following sentence in the beginning of he proof's chapter:


  The following proof based on ideas given by Iosif Pinelis in a proof on mathoverflow.com [1]


([1] points to the reference of Pinelis' answer in the bibliography of my thesis)

Do I need to cite Pinelis' answer whenever I use a notation/an idea of his post (it might be hard to tell afterwards, which are my original ideas and which ideas comes from his post)?

Thanks in advance for your answers!
First, I would modify your sentence as (Mathoverflow etc. goes into the bibliography):


  The following proof is based on the ideas given by Iosif Pinelis [1].


Then,


  Do I need to cite Pinelis' answer whenever I use a notation/an idea of his post?


For the notation, you can make an addition to the sentence above (but explain the notation in the appropriate place):


  The following proof is based on the ideas given by Iosif Pinelis [1]. The notation employed in this section shall follow closely that of the cited work (or some equivalent sentence).


Instead, when using an idea, yes, I would put again the reference "[1]".