 A third book was later mentioned by Mohr's son; for many years this was believed to be the "Gegenübung auf Compendium Euclidis Curiosi" but argue that it must be a different book, and that the "Gegenübung" has a different author.As well as his work on geometry, Mohr contributed to the theory of nested radicals, with the aim of simplifying Cardano's formula for the roots of a cubic polynomial.While in the Netherlands, Mohr became a friend of Ehrenfried Walther von Tschirnhaus.