The Wikipedia article on association schemes claims regarding Bose-Mesner algebras:
There is another algebra of $\left(n+1\right)\times \left(n+1\right)$ matrices which is isomorphic to ${\mathcal {A}}$, and is often easier to work with.
What is this algebra called? In which paper(s) is it defined and used? Unhelpfully, the statement is not cited.