Erratum: analytic equilibria with quadrupole symmetry in the paraxial limit

In Eq. (43) the third and fourth terms on the left-hand side of the equation should be preceded by minus signs, as should the right-hand side of Eq. (55). In the first equation on page 1330 the factor exp(i theta') should be exp(2i theta'). These errors are typographical only and have no effect on the remainder of the paper. An algebraic error appears in Eq. (46): the first term on the right-hand side should be preceded by a minus sign, which requires that the right-hand sides of Eqs. (71) and (B1) also be reversed in sign. The effect of this change is to reverse the sign of the octupole component of the flux-surface distortion, causing the square-shaped equilibrium flux surfaces shown in the original version of the paper (Fig. 7) to become diamond-shaped as in the accompanying figure. Finally, the terms normal and geodesic curvature were used in a manner that does not conform to accepted mathematical usage.