  Recent progress in holographic correspondence uncovered remarkable relations
between key characteristics of the theories on both sides of duality and
certain integrable models. In this note we revisit the problem of the role of
certain invariants in low-dimensional holography. As motivating example we
consider first the entanglement entropy in 2d CFT and projective invariants.
Next we consider higher projective invariants and suggest generalization to
higher spin theories. Quadratic in invariants deformations is considered and
conjectured to play role in low-dimensional higher spin holography.
