GD152/21 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 21-09-35N 115-18-22E，21-09-25N 115-19-34E，21-08-42N 115-20-10E，21-08-04N 115-20-02E，21-05-34N 115-19-07E，21-05-32N 115-15-04E AND 21-09-19N 115-15-02E FROM 17 JUL. TO 30 OCT. SIGNAL LIGHTS AND SHAPES WILL BE EXHIBITED ADVISED TO AVOID GUANGDONG MSA CHINA