  Fuchsian differential equations of order 3 with three singular points and
with an accessory parameter are studied. When local exponents are generic, no
shift operator is found, for codimension-1 subfamilies, neither. We found shift
operators for several codimension-2 subfamilies of which accessory parameter is
assigned as a cubic polynomial in the local exponents. The Dotsenko-Fateev
equation is one of them.
