Notes for BBS/Archibald-080709-110259.jpg

Warning. The first term in the definition of $C$, written on the blackboard as the identity matrix $I$, should really be the diagonal matrix whose $jj$ entry is $-s_{j}d_{j}$. Thus the $C$ in the example should be $C={\begin{pmatrix}-1&0&0\\-1&1&1\\0&1&1\end{pmatrix}}$.