The site is here and there also also one or two other articles on the Daily Telegraph (UK) site at WWW.TELEGRAPH.CO.UK.If you seriously(!!!) want to know more about the maths / physics of flutes then it might be worth gettin touch with my friend Alan Muhr at muhr@rubber.demon.co.uk. Alan has been making flutes for some time from sink overflow pipes from mathematical first principles. The equations for simple linear bore pipes with the holes the same size go into 4 or 5 pages, but he has got beyond that ...
Hope this is helpful.
Cheers!
Ian