  These are lecture notes of the Summer school on the geometry of differential
equations held in Nordfjordeid, Norway in 1996. They cover geometric structures
related to scalar second order ODEs, the construction of the associated Cartan
connection, techniques for computing invariants of differential equations
starting from the Cartan connection, recognition of symmetric 2nd order ODEs by
their differential invariants and the constructive aspects of the local
equivalence problem.
