In this paper we initiate a general classification for Lie algebras of order
3 and we give all Lie algebras of order 3 based on sl(2,C)
and iso(1,3) the Poincar\'e algebra in four-dimensions. We then
set the basis of the theory of the deformations (in the Gerstenhaber sense) and
contractions for Lie algebras of order 3.Comment: Title and presentation change