  An explicit operator mapping in the form of a similarity transformation is
constructed between the RNS formalism and an extension of the pure spinor
formalism (to be called EPS formalism) recently proposed by the present
authors. Due to the enlarged field space of the EPS formalism, where the pure
spinor constraints are removed, the mapping is completely well-defined in
contrast to the one given previously by Berkovits in the original pure spinor
(PS) formalism. This map provides a direct demonstration of the equivalence of
the cohomologies of the RNS and the EPS formalisms and is expected to be useful
for better understanding of various properties of the PS and EPS formalisms.
Furthermore, the method of construction, which makes systematic use of the
nilpotency of the BRST charges, should find a variety of applications.
