Subresultants of primitive polynomials

Given two primitive polynomials $f,g\in D[x]$ over some domain $D$, is there anything we can say about the primitiveness of their $i$-th subresultant polynomials $Sres_i(f,g)$? I.e. is there a simple way to determine the content of $Sres_i(f,g)$, and in particular is it always 1?

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I'm familiar with the resultant of two polynomials, but not with subresultants. Can you meet us halfway? –  Gerry Myerson Aug 4 '11 at 0:33