diff --git a/Test-problems.md b/Test-problems.md
index 3b788f7..92bd291 100644
--- a/Test-problems.md
+++ b/Test-problems.md
@@ -122,16 +122,38 @@ Rhombic ring of icosahedra
 - **Author:** RobertLovesPi
 - **Published:** [“A Rhombic Ring of Icosahedra, Leading to a Rhombic Dodecahedron Made of Icosahedra.”](https://robertlovespi.net/2015/09/15/a-rhombic-ring-of-icosahedra-leading-to-a-rhombic-dodecahedron-made-of-icosahedra/) RobertLovesPi.net (September 15, 2015).
 
+Almost-ring of 48 tetrahedra
+
+- **Author:** Ian Stewart
+- **Published:** “Steinhaus’s Problem on Chains of Regular Tetrahedra.”
+
+Quadrahelix and octahelix
+
+- **Author:** Michael Elgersma and Stan Wagon
+- **Published:** “The Quadrahelix: A Nearly Perfect Loop of Tetrahedra.” [`arXiv:1610.00280`](https://doi.org/10.48550/arXiv.1610.00280) (November 7, 2016).
+
+Almost-ring of thirteen square anti-prisms
+
+- **Author:** Jim McNeill
+- **Published:** [“A ring of anti-prisms”](https://www.orchidpalms.com/polyhedra/acrohedra/nearmiss/aprism-rings.html). [Polyhedra](https://www.orchidpalms.com/polyhedra/).
+
 #### Statement
 
-Choose a rigid ring of polyhedra. Assemble it by constraining distances between vertices or angles between faces.
+Choose a rigid ring or almost-ring of polyhedra. Assemble it by constraining distances between vertices or angles between faces. If it's a ring, verify that it closes and is rigid. If it's an almost-ring, verify that it doesn't close.
 
 #### Notes
 
 Here are some examples of interesting rings:
 
 - A ring of eight dodecahedra
-- A [rhombic ring](https://robertlovespi.net/2015/09/15/a-rhombic-ring-of-icosahedra-leading-to-a-rhombic-dodecahedron-made-of-icosahedra/) of eight icosahedra
+- [A rhombic ring of eight icosahedra](https://robertlovespi.net/2015/09/15/a-rhombic-ring-of-icosahedra-leading-to-a-rhombic-dodecahedron-made-of-icosahedra/)
+
+Here are some examples of interesting almost-rings
+
+- An almost-ring of 48 tetrahedra (Stewart 2023, Figure 2)
+- A quadrahelix almost-ring of tetrahedra (Wagon and Elgersma, 2016)
+- An octahelix almost-ring of tetrahedra (Wagon and Elgersma, 2016)
+- [An almost-ring of thirteen square anti-prisms](https://www.orchidpalms.com/polyhedra/acrohedra/nearmiss/aprism-rings.html)
 
 ## Exploring configuration spaces