2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/124092A classical link in 3-space can be represented by a Gauss paragraph encoding a link diagram in a combinatorial way. A Gauss paragraph may code not a classical link diagram, but a diagram with virtual crossings. We present a criterion and a linear algorithm detecting whether a Gauss paragraph encodes a classical link. We describe Wirtinger presentations realizable by virtual link groups.12 pages, 12 figures, v2: new results have been addedGeometric TopologyGroup Theory57M25; 20F05text