In this paper we describe a simple method for obtaining a classification of small-dimensional solvable Lie algebras. Using this method, we obtain the classification of three- and four-dimensional solvable Lie algebras (over fields of any characteristic). Precise conditions for isomorphism are given.
"Classification of Solvable Lie Algebras." Experiment. Math. 14 (1) 15 - 25, 2005.