Tosco Corp., an oil refiner headquartered in...

Tosco Corp., an oil refiner headquartered in Santa Monica, said it has reached an agreement with a group of investors to limit their purchase of equity in the company to 20% of its shares of common stock. Tosco disclosed the agreement with Argus Energy of Stamford, Conn., in a proxy mailed Thursday to shareholders. The company said Argus, headed by Thomas O’Malley, former vice chairman of Salomon Inc., began acquiring shares in Tosco about two months ago. Tosco said its management reached a standstill agreement that will remain in effect for a year. Company officials described it as “buying some time� to avert a hostile move by Argus, which was also granted the two board seats it asked for.