Paradromic Rings
Rings produced by cutting a strip that has been given 
half twists and been re-attached into 
equal strips(Ball and Coxeter 1987, pp. 127-128).
References
Ball, W. W. R. and Coxeter, H. S. M. Mathematical Recreations and Essays, 13th ed. New York: Dover, pp. 127-128, 1987.
- Harmonic Analysis
- Harmonic Brick
- Harmonic Conjugate Function
- Harmonic Conjugate Points
- Harmonic Coordinates
- Harmonic Decomposition
- Harmonic Divisor Number
- Harmonic Equation
- Harmonic Function
- Harmonic-Geometric Mean
- Harmonic Homology
- Harmonic Logarithm
- Harmonic Map
- Harmonic Mean
- Harmonic Mean Index
- Harmonic Number
- Harmonic Progression
- Harmonic Range
- Harmonic Ratio
- Harmonic Segment
- Harmonic Series
- Harmonic System of Points
- Harmonious Graph
- Harnack's Inequality
- Harnack's Theorems