If any one can provide some weblinks or any ebook extracts on how to sketch nonlinear GLOBAL phase portraits of 2D system ..plz....

i am talking about the methods where u first plot the x' = 0 and y' = 0 equatiions.....which divide the plane in number of regions....then u find the signs of x' and y' in all those regions etc......and so on and so on...with reasonings why the separatracies will not cross over to certain regions etc etc..

it would be great if there was a well solved example in such way???

any help will be highly appreciated.....thank you