2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/140530We provide new information about the structure of the abelian group of topological concordance classes of knots in $S^3$. One consequence is that there is a subgroup of infinite rank consisting entirely of knots with vanishing Casson-Gordon invariants but whose non-triviality is detected by $L^{(2)}$ signatures.26 pages, 3 figuresGeometric Topologytext