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.