方便查询的编号，标记，索引；A reference is something such as a number or a name that tells you where you can obtain the information you want.
//…a map reference…
地图索引
Make a note of the reference number shown on the form.
把表格上的编码记下来。
引语；引用的观点；引证；A reference is a word, phrase, or idea which comes from something such as a book, poem, or play and which you use when making a point about something.
//…a reference from the Quran.
引自《古兰经》的引文
//…historical references.
历史引证