The Sensex at the Bombay Stock Exchange declined 51 points, or 0.3 percent, to close at 18,619, after a special, 75 minute, muhurat trading session from 3.45 p.m. to 5 p.m., today. Stocks fell on profit-booking by investors, amid weak global markets. The Nifty at the National Stock Exchange lost 17 points, or 0.3 percent, to 5,667.Stock markets in Japan, China, Hong Kong, and South Korea lost between 0.2 percent and 1.5 percent.