This is a question about the correct reference for a result that seems to appear frequently in the literature on planar graph isomorphism. In A $V \log V$ Algorithm for Isomorphism of Triconnected Planar Graphs, Hopcraft and Tarjan mention that a 3-connected planar graph has an essentially unique embedding into the plane (up to mirror symmetry), and attribute this result to Whitney (1933) A set of topological invariants for graphs. I've noticed this citation reappearing in various places (for example here, here, and here), but I couldn't find the result in Whitney's article itself -- am I just overlooking something? The paper is dense, and builds on a series of other articles he published in succession... Still, this result sounds a lot like Theorem 11 of Whitney (1932) Congruent Graphs and the Connectivity of Graphs, which states that a 3-connected planar graph has a unique dual. Was that the intended reference?
reference clarification: Whitney's theorem on unique embeddability of 3-connected planar graphs?
reference request;graph theory;planar graphs;ho.history overview