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    List colorings of edge-critical graphs
Conjecture   Suppose that  is a
 is a  -edge-critical graph. Suppose that for each edge
-edge-critical graph. Suppose that for each edge  of
 of  , there is a list
, there is a list  of
 of  colors.  Then
 colors.  Then  is
 is  -edge-colorable unless all lists are equal to each other.
-edge-colorable unless all lists are equal to each other. 
 is a
 is a  -edge-critical graph. Suppose that for each edge
-edge-critical graph. Suppose that for each edge  of
 of  , there is a list
, there is a list  of
 of  colors.  Then
 colors.  Then  is
 is  -edge-colorable unless all lists are equal to each other.
-edge-colorable unless all lists are equal to each other. (Reproduced from [M].)
A graph  is said to be
 is said to be  -edge-critical if it is not
-edge-critical if it is not  -edge-colorable but every edge-deleted subgraph is
-edge-colorable but every edge-deleted subgraph is  -edge-colorable. (Here
-edge-colorable. (Here  is the maximum degree of
 is the maximum degree of  .)
.)
Bibliography
*[M] B. Mohar, Problem of the Month
* indicates original appearance(s) of problem.
 
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