Otto J. Karst, Semi-Complex Functions and Their Graphs, Mathematics Magazine, Vol. 35, No. 5 (Nov., 1962), pp. 282-288 ...

All quadratic functions have the same type of curved graphs with a line of symmetry. The graph of the quadratic function y = a x 2 + b x + c is a smooth curve with one turning point.

We develop parametric classes of covariance functions on linear networks and their extension to graphs with Euclidean edges, that is, graphs with edges viewed as line segments or more general sets ...