Where to put #include/script src statement

This will probably be a confusing question, but I'm going to give it a shot.

In my panel development, I use the PProPanel as a base to start developing. 

In that 'package', I have:

ext.js

index.html

PProPanel.jsx

Premiere.jsx

plus other files and folders.

In my development, I have created a library of custom functions that I use across multiple panels.

(example: myPProFunctions.js, myAEFunctions.js, myCommonFunctions.js)

I add this to individual panels by using an #include line, usually in the Premiere.jsx or the AE.jsx.

However, I've created some library functions that I can utilize in the ext.js and index.html.

My question is, where do I add the #include or the script src line so the libraries can be utilized across all files?

I've found that when I add the #include line to the Premiere.jsx file the ext.js file can't see the functions.

thanks for any input,

Kelly