Here is one of the better articles I've found, offering a perspective on heterodox baptism and sacramental economy opposed to that featured in the article by Archmandrite Ambrosius which I posted a link to on a recent thread.
A Response to Bishop Tikhon...
Admittedly, I will have to read and re-read this article carefully, as in many cases of presenting patristic witnesses, it's easy to confuse commentary with what the Father (or Holy Canon) is actually saying. However, I post the article to give the other side on this issue.
Seraphim