We know that in regular economies general equilibrium theory predicts a finite and odd number of equilibria, using the properties of the excess demand function and the index theorem.
How about the non-regular economies? From my understanding, these are the economies in which at least one price vector equilibirum generates a singular matrix of price effects. Geometrically, this can be interpreted as the excess demand function having a zero slope at one of the equilibria as shown in the picture below
Can we say something more about the equilibria, in case they are a finite number? Do they need to be even, odd or there is no restriction?