Links:Reactionless propulsion


 * The physics classroom Momentum and its conservation


 * Mathpages What is an Inertial Coordinate System?


 * Reflections on Relativity First principles


 * NASA Conservation of momentum

Typical opinion in the Russian blog about the gravitsapa:


 * "Гравицапа" генерала Меньшикова - заблуждение или попытка попасть в федеральную программу? Журнал Луки Мудищева, 4 Feb. 2010. (In Russian. Entlish translation of the title: "Gravitsapa" by general Menshikov – is it an error or an intent to enter the federal program?)