Zhihua Shen and Yafeng Xia 9 along the Sino-Indian border in 1959 also delayed surveying and delimiting boundaries in other areas. Liaoning and Jilin provinces were instructed to conduct research on the Sino-Korean border.In January and December 1959,the Liaoning authorities submitted information on the Sino- Korean border and a report on the inundated area caused by the Shuifeng reservoirs of the Yalu River.In March and December. Jilin province submitted one report on the Sino-Korean and Sino- Soviet borders and another report on findings regarding the inun- dated area in Ji'an county.In March 1960 the boundary commission of the State Council responded to Jilin province's queries regarding the Sino-Korean border.It agreed to Jilin's pro- posal that the center line of the Yalu River be the security line of border defense between China and North Korea.The commission also addressed the question of how to divide defense duties on the Sino-Korean border bridge.According to the records of a joint conference of Chinese representatives from the Ministry of Public Security and North Korean representatives from the Interior Min- istry on June 8,1955,in addition to provisional agreements on defense of the bridges in the Andong(Dandong)-Sinuiju area,the chief representatives and the deputies of both sides should decide on specific cases and define outpost areas for defense duty (Jilin Provincial Archive,folder 77-6-12).We have yet to find the details of the Jilin provincial boundary small group's report to the State Council boundary commission.But from the responses of the boundary commission,it was likely that the Chinese govern- ment started to consider the issue of delimiting boundary lines along the source area of the Tumen River. A State Council boundary commission document dated March 14,1960,states that China's borders with socialist neighbors were relatively stable in 1959.The document discussed three categories of border issues.It said there had been no major disputes although unresolved border issues remained;unresolved border issues remained and new issues had emerged;and in some cases,even though agreement had been reached to resolve border issues,new issues had emerged and old disputes remained unresolved.The Sino-Soviet border issue belonged to the first category while the Sino-Mongolian border issue belonged to the third category.The