内地: inland; interior; hinterland 短语和例子内地城市 inland city; 发展内地工业 promote the inland industry; 在中国内地旅游 travel in the interior of china; 内地工业 industry in the interior; 内地海关 inland custom house; 内地
书信往来: keep on shuttlecocking letters; keep up regular correspondence with sb.: 常有书信往来 keep up a regular correspondence