These are very helpful and can be used to discover the origin of the document, such as the collection (SRC: col) and key (SRC: key).

这些属性非常有用，可以用来发现文档的出处，例如集合(src： col)和键(src： key)。

youdao

Mr Belhadj, a key brigade leader in the 2011 toppling of Col Gaddafi, plans to run in elections next month.

BBC: Libya's Belhadj quits military post for politics