 Complete the following phrase:  Other aspects of the Syrian conflict uncovered and documented by Higgins include the use of cluster bombs in 2012, which the Syrian government denied using; the proliferation of shoulder-launched heat-seeking missiles known as MANPADS; and the proliferation of Croatian-made weapons which was reportedly connected to the United States, a story later picked up by The New York Times. He has also investigated the Syrian regimes alleged use of chemical weapons, including the 