  The next period is that of 1872–1878, in which he wrote his two most famous papers: (1872) (Weitere Studien) and (1877b) (Über die Beziehung). The 1872 paper contained the Boltzmann equation and the H-theorem. Boltzmann claimed that the H-theorem provided the desired theorem from mechanics corresponding to the second law. However, this claim came under a serious objection due to Loschmidt's criticism of 1876. The objection was simply that no purely mechanical theorem could ever produce a time-asymmetrical result. Boltzmann's response to this objection will be summarized later.