We have the following indirect implication of form equivalence classes:
			
| Implication | Reference | 
|---|---|
| 89 \(\Rightarrow\) 90 | The Axiom of Choice, Jech, 1973b, page 133 | 
| 90 \(\Rightarrow\) 118 | Horrors of topology without AC: A non-normal orderable space, van Douwen,  E.K. 1985, Proc. Amer. Math. Soc. | 
Here are the links and statements of the form equivalence classes referenced above:
| Howard-Rubin Number | Statement | 
|---|---|
| 89: | Antichain Principle: Every partially ordered set has a maximal antichain. Jech [1973b], p 133. | 
| 90: | \(LW\): Every linearly ordered set can be well ordered. Jech [1973b], p 133. | 
| 118: | Every linearly orderable topological space is normal. Birkhoff [1967], p 241. | 
Comment: