Chronological footnotes in InDesign Book Doc

Hi all, first time poster here.

I am using InDesign CS6 on a PC.

I am trying to create an InDesign Book, with multiple documents (will be more than 40 when complete). I need the footnote to be chronological throughout the document, so start at 1 and not restart every page, section, document etc.

This is my first attempt at a 'Book' document, usually we just work with individual documents and thread text frames to make the footnotes work chronologically.

I've searched a number of help, tutorial and forum pages with no success.

If you have an answer, or know of where an answer can be found I would appreciate it.

I am a self taught InDesign user, so would appreciate detailed solutions.

Thank you.

Dale