3ZHOU Yingxin, ZHAO Jian. Assessment and planning of underground space use in Singapore [ J ]. Tunnelling and Underground Space Technology,2016,55 (5) : 249 - 256.
4Hunt D V L, Nash D, Rogers C D F. Sustainable utility placement via Multi-Utility Tunnels [ J ]. Tunnelling and Underground Space Technology,2014,39( 1 ) : 15 -26.