Era
20th century
40
19th century
12
20th century --
8
1945-
6
1933-1945
5
1871-1918
4
1918-1933
4
20th century. --
4
1949
3
20th century - Juvenile literature
3
United States
3
16th century --
2
18th century
2
1911-1949
2
1917
2
1917-1921
2
1918-1945
2
1920-1929
2
1925-1953
2
1942 - 1945
2
1942-1949
2
1948-1960
2
1949-
2
1949-1976
2
1971-1990
2
1975-
2
1990-
2
20th Century
2
Australia
2
Japanese occupation, 1942-1945
2
Republic, 1912-1949
2
1478-1798
1
1642-1727 - Knowledge - Science - Congresses
1
1642-1727. Principia - Congresses
1
16th century
1
1750 - 1918
1
1775 - 1783
1
1783 - 1789
1
17th century
1
1801-1917
1
1801-1917 - Sources
1
1812-1870 --
1
1819-1975
1
1853-1910
1
1857-1919
1
1861 -1912
1
1861-1865
1
1867-1918
1
1868-
1
1894-1917
1
more ...