Immanuel Kant
Kant developed his moral philosophy in three works: "Groundwork of the Metaphysic of Morals" (1785), "Critique of Practical Reason" (1788), and "Metaphysics of Morals" (1797).
German idealism
Karl Leonhard Reinhold published two volumes of "Letters Concerning the Kantian Philosophy" in 1790 and 1792. They provided a clear explication of Kant's thoughts, which were previously inaccessible due to Kant's use of complex or technical language.