Multiple Reference Tool

USES:
Unlike Maya's default file reference window, this tool allows you to select more than one file at a time. Also by adding more file rows in the tool UI you can make references for files located in different folders all at once. It enables you to reference one file multiple times in one go and assign a namespace of your choice.

INTERFACE:
Use the "browse" button on the right of each row to select the files you want to reference (you can shift/ctrl select multiple files). Type the desired number of copies  in the "Qty" field and the desired namespace in the "Namespace" field.

Use the "Add file row" button towards the bottom of the UI to add as many rows as you need. You'll need different rows to browse for files that live in different folders, or if you want to assign different quantities or namespaces for different files.

When all your preferences are set click on "Create references" to reference all the files.

INSTALLATION:

To get the this tool download the script file and save it in your maya/version/scripts folder:

lr_referenceTool.py

Then run the following code in the script editor (make sure to be in a python tab):
import lr_referenceTool
reload(lr_referenceTool)

You can save these lines in a shelf button for easy access.

If you don't want to download the file you can just copy the code below to the script editor and drag it onto your custom shelves so you can access it at any time (remember to save your shelves before quitting Maya)