The Reference menu option allows you to access mathematical expressions from another document. Expressions are referenced using Equation Labels.

To insert a reference from another document:

In the document you want to reference, determine which label refers to the expression to be referenced. For example, in the image below, the reference will be the equation label (1).

In the main document, from the Insert tab of the ribbon, in the Reference group, click Reference( ). A file selector dialog opens.

Select a file containing the expression to be referenced. The Select Equation dialog opens.

Select a reference and click OK. The reference is the equation label within that document. The output from the reference is inserted into your document.

If you are using Document mode, the command that is inserted will be hidden in a collapsed document block.

Behind the scenes this command retrieves the referenced output.

Another way to reference one document from another is by using a Maple workbook.  A Maple workbook is a way to assemble multiple files together into a single file.  It makes it easy to reference data or calculations from an attached file, including from another Maple document.  For details, see The Workbook File Format.