Uppal, S. M.2012-10-302012-10-301984INT. J. MATH. EDUC. SCI. TECHNOL., 1984, VOL. 15, NO. 2, 149-152http://ir-library.ku.ac.ke/handle/123456789/5882Publisher version (Taylor & Francis) available at http://dx.doi.org/10.1080/0020739840150202enArticle