O. Kirimi, Denis, Mercy Wanja, Hilary Barchok, and Nelson Jagero. 2017. “Effectiveness of Integrating Science Process-Skills in Teaching Mathematics on Students’ Achievement in Secondary Schools in Tharaka-Nithi County, Kenya”. International Journal of Academic Research in Progressive Education and Development 6 (4). https://ijarped.com/index.php/journal/article/view/360.