Corrigendum: The symplectic sum formula for Gromov-Witten invariants

We correct an error and an oversight in [IP]. The sign of the curvature in (8.7) is wrong, requiring a new proof of Proposition 8.1. Also, several lemmas addressed only the basic case of maps with intersection multiplicity s=1; the general case follows by applying the pointwise estimates in [IP] with a modified Sobolev norm. These corrections do not affect the results of the paper. We thank M. Tehrani and A. Zinger for pointing out these issues.