Many kinds of algorithms of continued fraction expansions of dimension s(≥ 2) have been studied starting with K.G.J.Jacobi(1804-1851), for example, see [14]. For s = 1, we know Lagrange’s theorem related to periodic continued fractions and real quadratic irrationals. But, even for real cubic irrationalities, there appeared no suitable algorithms (of dimension 2). In this section, we roughly exp...