Is there a provably better way, though? I think this was basically the premise of the original question: Given that there is doubt about the safety of some PRNG

Is there a provably better way, though? I think this was basically the premise of the original question: Given that there is doubt about the safety of some PRNG scheme, is there a proven way to combine multiple PRNG scheme with the property that the resulting PRNG is at least as secure as the most secure "input" PRNG? If there is such a better way, then please provide more information - links and such.