>\addtolength{\baselineskip}{1.ex}
>\english
>\mathenumber
>\begin{englishabstract}
>
>In this thesis we have collected some of the results in list colrings
>of graphs. Suppose that we have assigned some lists (sets) of colors
>to the vertices of a graph $G$. By a list coloring for $G$ (from the
>assigned lists) we mean a proper coloring in which each vertex takes
>on a color from its own list. The thesis is divided into four chapters,
>namely choosability, unique list coloring, list critical graphs, and
>some applications.
>
>In the first chapter, we cite a theorem of Erd\"os, Rubin, and
>Taylor, which characterizes 2--choosable graphs. We also cite a theorem
>of S.~Gravier which constructs all graphs who are~not $k$--choosable.
>Finally we narrate the well known List Coloring Conjecture~(LCC), which
>claims that the chromatic and list chromatic indices of each graph are
>the same. We quote some of the progresses made towards proving this
>conjecture.
>
>In the second chapter, we cite some characterization
>theorems, and we give the proof of a theorem which relates the concepts of
>uniquely colorability and uniquely list colorability.
>
>In the third chapter, we study the concept of list critical graphs. We cite
>a theorem which characterizes list critical graphs with list chromatic
>number~3. We also cite a conjecture concerning the concept of list
>criticality, which is equivalent to the~LCC.
>
>\englishkeywords{graph coloring, list coloring, uniquely colorable graphs,
>uniquely list colorable graphs, critical graphs, list critical graphs}
>\end{englishabstract}
>\farsi
>\addtolength{\baselineskip}{-1.ex}