Remarks on the three-level topological string theories

A few observations concerning topological string theories at the string-tree level are presented: (1) The tree-level, large phase space solution of an arbitrary model is expressed in terms of a variational problem, with an ''action'' equal, at the solution, to the one-point function of the puncture operator, and found by solving equations of Gauss-Manin type; (2) For Ak Landau-Ginzburg models, an extension to large phase space of the usual residue formula for three-point functions is given. (author)