@online{olson2026,
  author = {Olson, Dieter},
  title = {Classic {Sources} of {Nonlinearity} in {Mechanical}
    {Systems:} {A} {Comprehensive} {Review} for the {Control-Affine}
    {Framework}},
  date = {2026-03-10},
  url = {https://affinedrift.com/articles/sources-of-nonlinearity.html},
  langid = {en}
}