Authors:

As a rule, so-called "positional" sacrifices are considered more difficult, and therefore more praise-worthy, than those which are based exclusively on an exact calculation of tactical possibilities.

Alexander Alekhine, Garry Kasparov (2011). “Alexander Alekhine's Best Games: Algebraic edition”, Pavilion Books
As a rule, so-called positional sacrifices are considered more difficult, and therefore more praise-worthy, than those which are based exclusively on an exact calculation of tactical possibilities.