How does this 100W 12V to 220V inverter circuit using transistors work?

Who can tell me how does this circuit work, please !

"http://www.eleccircuit.com/wp-content/uploads/2007/04/circuit-inverter-100w-12v-to-220v-by-transistor.jpg(picture)":http://www.eleccircuit.com/wp-content/uploads/2007/04/circuit-inverter-100w-12v-to-220v-by-transistor.jpg

or you can give me a few related books
thank in advance !

source: http://www.eleccircuit.com/inverter-12v-to-220v-100w-transistor/

This is simple bistable multivibrator feeding a driver/wave-shaping circuit that in turn drives a class-B output stage whose load is a step-up transformer. The transformer is simply a standard 12-0-12V transformer connected in reverse - the primary rating depends on whether you want 110V or 220V.

The idea is simple, generate a 50 Hz square wave, shape it to somewhat resemble a sine wave (or more probably a triangular wave, with its tops chopped off slightly), then feed it to a low voltage/high current o/p stage that drives the reverse connected mains transformer.

could you tell clearly about two transistors Q3 and Q4. or would you give me some related books, i can read myself :)

thank pro,