Among your remaining un-margined assets, you might need to sell some stocks and add some bonds and cash to keep your risk at the overall level you desire.

WSJ: The Intelligent Investor: Borrowing Against Yourself

The lesson is that diversification might help smooth out routine fluctuations, but under extreme conditions your risk level is likely to depend very much on the overall economic exposure of your holdings.

FORBES: 4 New Rules for Asset Allocation

There was, in fact, a vigorous debate within Goldman about the right level, just as there was over the firm's overall risk levels.

ECONOMIST: The firm that came to dominate world finance