  Canonical forms of boundary conditions are important in the study of the
eigenvalues of boundary conditions and their numerical computations. The known
canonical forms for self-adjoint differential operators, with eigenvalue
parameter dependent boundary conditions, are limited to 4-th order differential
operators. We derive canonical forms for self-adjoint 2n-th order differential
operators with eigenvalue parameter dependent boundary conditions. We compare
the 4-th order canonical forms to the canonical forms derived in this article.
