The Insert>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 menu, select 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.