This book presents the extensions to the quaternionic setting of some of
the main approximation results in complex analysis. It also includes the
main inequalities regarding the behavior of the derivatives of
polynomials with quaternionic cofficients. With some few exceptions, all
the material in this book belongs to recent research of the authors on
the approximation of slice regular functions of a quaternionic variable.
The book is addressed to researchers in various areas of mathematical
analysis, in particular hypercomplex analysis, and approximation theory.
It is accessible to graduate students and suitable for graduate courses
in the above framework.