PIE Sound changes

Daniel A. Wier spake, saying:

> (Thanks to Christopher Gwinn, who has a fairly exhaustive list of PIE roots
> at his website: http://members.xoom.com/_XMCM/piestudies/index.htm.)
I have a question concerning the Morphology chart. In several instances, the
chart indicates multiple sound changes (e.g. PIE "B" -> Gaulish "B/M/U"). I
assume these are conditional, but does anyhone know if there is anywhere
that I can find out what those conditions were?

Thanks,

John