After gaining 410 points in the previous three sessions, the Sensex at the Bombay Stock Exchange rose 77 points, or 0.4 per cent, to 20,137 in opening trade, today, on sustained buying by funds, amid positive Asian bourses. After paring some of its early gains, the Sensex stood 49 points, or 0.2 percent in the green, at 20,109, a short while ago. Key stock indices in Hong Kong, Indonesia, South Korea, Singapore and Taiwan were up by between 0.1 percent and 0.5 percent, today. In the US, the Dow Jones Industrial Index had ended 0.5 per cent higher, overnight.