Аннотация:
We show how the recently again discussed $N$-point Witt, Virasoro,
and affine Lie algebras are genus zero examples of the multi-point versions of Krichever–Novikov
type. These multi-point versions were introduced and studied by Schlichenmaier. Using this more general point of view, useful structural insights and an easier access to calculations can be obtained. The concept of almost-grading will yield information about triangular decompositions which are of importance in the theory of representations. The algebra of functions,
vector fields, differential operators, current algebras, affine Lie algebras, Lie superalgebras and their central extensions show up.
As special example the three-point case is given.
