Belyi functions are maps from Riemann surfaces to CP1 ramified exactly at three points. Four point Virasoro conformal block on a sphere as a function of the cross-ratio x is believed to posses singularities only at three points. My question is whether the generic four-point Virasoro conformal block on a sphere is a Belyi function? I am also quite interested in references where conformal blocks might be analysed from this point of view.