A method and apparatus for superimposing printed characters of any such nature as may be transmitted upon a received television image, at the will of the viewer at the receiver.Expand

Preliminaries. Categories. Functors. Diagrams. Naturality and Sketches. Products and Sums. Catesian Closed Categories. Finite Discrete Sketches. Limits and Colimits. More About Sketches. Fibrations.… Expand

We show that in order to obtain the theorem of Aczel and Mendler on the existence of terminal coalgebras for an endofunctor on the category of sets, it is entirely unnecessary to delve into such exotica as non-well-founded set theory.Expand

This paper is concerned with two problems which, although not apparently closely related, are solved in part by the same methods. The first problem is: given a bicomplete (=comple te and cocomplete)… Expand