\title{Chains of Recurrences for Functions of Two Variables and their
  Application to Surface Plotting}

\author{Olaf Bachmann\thanks{On research leave from Kent State University}\\
RIACA\\
Kruislaan 419, 1098 VA Amsterdam\\
The Netherlands\\
E-mail: \verb?obachman@mcs.kent.edu?}

\begin{abstract}
  The main aim of this paper is to show that Chains of Recurrences
  (CR's) have the potential to make computations of mathematical curves and
  surfaces considerably more efficient. For this, the concept of CR's
  is extended to trigonometric functions and functions of two
  variables. Algorithms for constructing and evaluating two-dimensional
  CR-expressions are given. A Maxima implementation of the considered
  method was successfully applied to the IZIC graphing
  tool.  Results and timings of the implementation are
  discussed in detail. 
\end{abstract}