GD138/21 SOUTH CHINA SEA GEOLOGICAL SURVEY WORK BY M/V “HAI YANG SHI YOU 708” “HAI YANG SHI YOU 709” AND “NAN HAI 503” IN AREA BOUNDED BY 20-32-11N 113-57-06E，20-32-40N 113-58-45E，20-32-05N 113-58-57E，20-30-31N 114-00-35E，20-30-33N 114-01-56E，20-28-07N 114-01-58E，20-28-04N 113-59-23E，20-29-23N 113-59-22E，20-30-44N 113-57-57E AND 20-30-38N 113-57-37E FROM 3 JUL. TO 30 OCT. SIGNAL LIGHTS AND SHAPES WILL BE EXHIBITED ADVISED TO AVOID GUANGDONG MSA CHINA