in this paper, the theorem is proved in which the layout of urban drainage pipe network systems must be a tree structure.
本文证明了城市排水管网系统最优布局为树状结构的定理;
no drainage entity may drain sewage into the urban drainage pipe network and its accessory facilities if it fails to obtain an urban drainage license.
未取得城市排水许可证书,排水户不得向城市排水管网及其附属设施排放污水。
article 3 to drain sewage into the urban drainage pipe network and its accessory facilities, a drainage entity shall apply for an urban drainage license in accordance with these measures.
第三条排水户向城市排水管网及其附属设施排放污水,应当按照本办法的规定,申请领取城市排水许可证书。