Barreno Layedra, N., 		Román Vargas, W., & 		Olalla Pilco, J.
(2017).
 Free mathematical software and its incidence in the learning  differential calculum.
<em>MktDESCUBRE, 1</em>(10), 103 - 110.
Retrieved from <a href="http://revistas.espoch.edu.ec/index.php/mktdescubre/article/view/147" target="_new">http://revistas.espoch.edu.ec/index.php/mktdescubre/article/view/147</a>