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	subroutine q2mat(qq,dd)
c
c  converts quaternion to matrix
c
	real qq(4),dd(3,3)
	real t1
c
	t1=qq(4)**2-qq(1)**2-qq(2)**2-qq(3)**2
	do 100, i=1,3
	do 90,  j=1,3
	dd(i,j)=0.
	if(i.eq.j) then
		dd(i,j)=dd(i,j)+t1
		endif
	dd(i,j)=dd(i,j)+(2.*qq(i)*qq(j))
	if(i.ne.j) then
		do 80, ijk=1,3
			if(i.ne.ijk.and.j.ne.ijk) k=ijk
80			continue
		kl=j-i
		if(kl.eq.2) kl=-1
		if(kl.eq.-2) kl=1
c  poor man"s permutation tensor!
		dd(i,j)=dd(i,j)-(2.*qq(k)*qq(4)*float(kl))
		endif
90		continue
100	continue
	return
	end
c
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c