Thomsen had formalized the Three-age System by the time of its publication in 1836. The next step forward was the formalization of the Palaeolithic and Neolithic by Sir John Lubbock in 1865. Between these two times Denmark held the lead in archaeology, especially because of the work of Thomsen's at first junior associate and then successor, Jens Jacob Asmussen Worsaae, rising in the last year of his life to Kultus Minister of Denmark. Lubbock offers full tribute and credit to him in "Prehistoric Times".