Bifurcation preserving discretisations of optimal control problems
C. Offen, S. Ober-Blöbaum, 54(19) (2021) 334–339.

Hamiltonian boundary value problems, conformal symplectic symmetries, and conjugate loci
R.I. McLachlan, C. Offen, New Zealand Journal of Mathematics 48 (2018) 83–99.