Complex sentence: He expanded on the work Niels Nörlund had done on Euler polynomials as a solution to a particular difference equation; in particular, Cox introduced generalised Euler polynomials and the generalised Boole summation formula as an expansion on the Boole summation formula.
Split into simpler sentences: He expanded on the work Niels Nörlund had done on Euler polynomials as a solution to a particular difference equation. Cox used generalised Euler polynomials and the generalised Boole summation formula to expand on the Boole summation formula.