常 駐 cháng zhù : resident; permanent (representative)

代 表 dài biǎo : representative; delegate; to represent; to stand for

首 席 shǒu xí : chief (representative, correspondent, etc)

首 席 代 表 shǒu xí dài biǎo : chief representative

議 員 yì yuán : member (of a legislative body); representative

眾 議 員 zhòng yì yuán : member of the US House of Representatives

眾 議 院 zhòng yì yuàn : House of Representatives (USA)