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It is a well‐known conjecture that if a regular graph G of order 2n has degree d(G) satisfying d(G) ⩾ n, then G is the union of edge‐disjoint 1‐factors. It is well known that this conjecture is true for d(G) equal to 2n—1 or 2n—2. We show here that it is true for d(G) equal to 2n — 3, 2n — 4, or 2n — 5. We also show that it is true for d(G) ⩾67|V(G)|.

In this paper we give a complete solution to the conjecture of Evans made in 1960 that if n-1 cells of an nxn matrix are preassigned with no element repeated in any row or column then the remaining n 2 -n+ 1 cells can be filled so as to produce a latin square. We in fact prove the stronger statement that n cells can be preassigned except in certain cases which we specify.

The graphs we consider here are either simple graphs, that is they have no loops or multiple edges, or are multigraphs, that is they may have more than one edge joining a pair of vertices, but again have no loops. In particular we shall consider a special kind of multigraph, called a star-multigraph: this is a multigraph which contains a vertex v*, called the star-centre, which is incident with each non-simple edge. An edge-colouring of a multigraph G is a map ø: E(G)→, where is a set of colours and E(G) is the set of edges of G, such that no two edges receiving the same colour have a vertex in common. The chromatic index, or edge-chromatic numberχ′(G) of G is the least value of || for which an edge-colouring of G exists. Generalizing a well-known theorem of Vizing [14], we showed in [6] that, for a star-multigraph G,where Δ(G) denotes the maximum degree (that is, the maximum number of edges incident with a vertex) of G. Star-multigraphs for which χ′(G) = Δ(G) are said to be Class 1, and otherwise they are Class 2.

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