Enhancing requirements engineering in agile methodologies by agent-oriented goal models : two empirical case studiesTenso, Tanel; Norta, Alexander; Rootsi, Hannes; Taveter, Kuldar; Vorontsova, Irina2017 IEEE 25th International Requirements Engineering Conference Workshops : proceedings2017 / p. 268-275 : ill http://doi.org/10.1109/REW.2017.24