1. 1. J. Vanek (1979 ) Time spent in howsework .Science. 12 May.
2. 2. K.E. Walker, and M.E. Woods (1976 ) Time Use: A Measurc of Household Production of Family Goods and Services . p.1 . Centre for the Family of the American Home Economics Association, Washington, DC.
3. 3. S.B. Linder (1970 ) The Harried Leisure Class . p.58 . Columbia University Press, New York.
4. 4. K.E. Walker, and M.E. Woods ,op. cit.