Xenakis and Messiaen: Because I couldn't find a picture of Messiaen and Varèse (it was always going to be a long shot). Taken from a 'Q & A' with James Dillon on The Arts Desk.
Varèse, whom I heard him [Messiaen] describe as 'my brother, who does for the urban landscape what I try to do with nature'.
Alexander Goehr: Finding The Key ('The Messiaen Class').
Also do check out this Varèse documentary extract on YouTube. Best thing I've seen on him so far but I can't find out where to get the full length film. Don't think it's the new Frank Schaeffer film Varese: The One All Alone (which I haven't seen, yet). Looks too dated but it's hard to tell with all the stock footage and YouTube compression etc.