http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
v.1: The early years, 1879-1902 -- v.2: The Swiss years, writings, 1900-1909 -- v.3: The Swiss years writings, 1909-1911 -- v.4: The Swiss years writings, 1912-1914 -- v.5: The Swiss years correspondencem, 1902-1914 -- v.6: The Berlin years, writings, 1914-1917
The Swiss years, correspondence 1902-1914