The superstring is quantized in a manner which manifestly preserves a U(5)
subgroup of the (Wick-rotated) ten-dimensional super-Poincare invariance. T
his description of the superstring contains critical N = 2 worldsheet super
conformal invariance and is a natural covariantization of the U(4)-invarian
t light-cone Green-Schwarz description. (C) 1999 Published by Elsevier Scie
nce B.V. All rights reserved.