The Binet-Pexider functional equation for rectangular matrices.
The Euler-Maclaurin sum formula for an inner derivation.
The geometry of convex cones associated with the Lyapunov inequality and the common Lyapunov function problem.
The local structure of the solutions of the multidimensional translation equation.
The matrix equation a(x...y) = a(x) + a(x)a(y) + a(y).
The stability of multiplicative semigroup homomorphisms to real normed algebras, I.