ZeTuer, Professor: Building the Square Circle ©Unknown, Professor Zetuer Softcover, comb-bound, 8.5x11", 32 pages

Image courtesy eBay seller M.ruetz

Comments: The Square Circle is one of the most deceptive production boxes ever created. This book covers different variations on building a square circle from a small table top size to a full fledged illusion large enough to produce your assistant. Available as an eBook from MagicGizmo.com.

Contents (from MagicGizmo site):

1 Square Circle Introduction
2 Basic Handling of the Apparatus
3 Black Art Material
4 Collapsible Square Circle
5 - How to Make It
6 -- Special Occasions
7 --- Spring
8 --- Christmas
9 --- Fourth of July
10 --- Halloween
11 --- Washington's Birthday
12 -- A Special Production Item
13 -- Additional Idea by Russ Walsh
14 Square Circle Project with Dimensions
15 - How to Build
16 - Performance
17 Square Circle Illusion
18 - Construction
19 - Performance
20 Cage-y Canister
21 Riedel Square Circle
22 Ultimate Square Circle with Bird Cage and Aquarium Production
23 - Aquarium
24 - Special Cage
25 - The Base
26 - Performance
27 Livestock Production
28 Phantom Tube Square Circle