Mason Gain Rule.

I need some help with Gain Rule theorem. I have some issue using the Signal flow as well. any tutorial or help will be appreciated.

 

http://www.teicontrols.com/notes/AutomaticControlsEE362K/MasonsRule.pdf

Is a short tech note on Mason's Gain rule

http://en.wikibooks.org/wiki/Control_Systems/Signal_Flow_Diagrams

is the signal flow.

These were the top two links when I googled ... http://www.google.com/search?hl=en&q=%2B%22mason+gain+rule%22

 

Thank you.