How can I balance the redox reaction of sulfur dioxide with oxygen?

How do I balance this reaction using half-redox equations? 
$$\ce{2SO2 + O2->2SO3}$$


My work is:


Oxidation: $\ce{SO2 + H2O -> SO3 + 2e- + 2H+}$


Reduction: $\ce{H2O + 2e- + O2 -> SO3 + 2H+}$


Total: $\ce{SO2 + 2H2O + O2 -> 2SO3 + 4H+}$


BUT it's false. What did I do wrong?




WELL I think you put something erroneous in your reduction formula. 


You will never get SO3 out of just O2 and water. Instead of SO3 


The reduction formla will be 4e- + O2 + 4H+ --> 2 H2O 


Multiply oxidation formula by 2 and add it to new reduction formula and you got your answer


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