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Resumen:
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Throughout his paper, the author uses "orientable manifold'' to mean a compact connected orientable 3-manifold without boundary. Such a manifold is known to be a ramified covering over a link of the 3-sphere, in which the ramification index of each singular point is ?2. If the covering has n leaves, suppose that there are m points of index 2 and 2m points of index 1; such a covering is of type (m,n?2m). The author's main theorem states: Every orientable manifold is a ramified covering of type (1,n?2).
He also uses the notion of a "link with a colouring of type (m,n?2m)''; these are intimately related to ramified coverings of type (m,n?2m). He conjectures that every link having a colouring of type (1,n?2) is "separable'', a term too complicated to define here. With this conjecture and his main theorem, he enunciates two further theorems and a second conjecture to show that his two conjectures, if true, would imply the Poincaré hypothesis for 3-manifolds. The author adds a note in proof to say that his first conjecture is false, as will be shown in a forthcoming paper by R. H. Fox. It therefore seems unnecessary to detail the conjectures in this review.
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