1. Draper, N. R., & Smith, H. Applied regression analysis (2nd ed.). New York: Wiley, 1981.
2. Goldberger, A. S. Econometric theory. New York: Wiley, 1964.
3. Hewlett-Packar. HP-67 standard pack. Corvallis, Ore: Author, 1976.
4. Texas Instruments. TI programmable 58/59 applied statistics. Austin, Tex: Author, 1977.