Era
20th century --
5
20th century
4
United States
4
1945-
2
1971-1981
2
1980-
2
1981-
2
1981-1993
2
20th century. --
2
1904-
1
1929 --
1
1943-
1
1945
1
1945 - 1970
1
1949-
1
1956-
1
1960-1980
1
1961-1971
1
1969-
1
1971-1990
1
1981
1
1985-1995
1
1989-
1
20th Century --
1
21st century --
1
Conduct of life
1
Psychology
1