Transition form factors of π0,η and η′ mesons: What can be learned from anomaly sum rule?

We studied the applications of the anomaly sum rule (ASR) to the transition form factors of light pseudoscalar mesons: π0,η and η′. This nonperturbative QCD approach can be used even if the QCD factorization is broken. The status of possible small non-OPE corrections to continuum in comparison to BaBar and Belle data is explored. The accuracy of the applied method and the role of the quark mass contributions are discussed.