Approximation theorems for the Moisil-Theodorescu system (Q1068245)

The authors prove a theorem of Runge type about approximation by regular polynomials for solutions of the so-called Moisil-Theodorescu system (which is not written down in the paper), this is a special case of regular functions in quaternions or in the Clifford algebra. Some applications of the Runge theorem are given. One should add to the literature chapter 3 of the book by \textit{F. Brackx}, \textit{R. Delanghe} and \textit{F. Sommen}, Clifford analysis (1982; Zbl 0529.30001) and the relevant papers cited there.