  The algebra of spacetime supersymmetry generators in the RNS formalism for
the superstring closes only up to a picture-changing operation. After adding
non-minimal variables and working in the "large" Hilbert space, the algebra
closes without picture-changing and spacetime supersymmetry can be made
manifest. The resulting non-minimal version of the RNS formalism is related by
a field redefinition to the pure spinor formalism.
