Janson, R[udolf]. August von (27.iv.1844-1917). Geschichte des Feldzuges 1814 in Frankreich. 2 vols. Berlin: E.S. Mittler, 1903-1905. Note: Vols. 6 7 of the series Series: Geschichte der Befreiungskriege, 1813-1815:

Vol 1 (1903):

http://books.google.com/books?id=SvU8AQAAIAAJ

Vol 2 (1905):

http://books.google.com/books?id=bPU8AQAAIAAJ

Short author bio (1906: see pp. 542-543:

http://books.google.com/books?id=MCkNAAAAIAAJ&pg=PA542

also

http://books.google.com/books?id=KLZWAAAAMAAJ&pg=PA71

Bio, see: Priesdorff: Soldatisches Führertum vol X (1937), pp. 76-78