Adnan, Z., J. Johari, H. S. Abdullah, and J. Ahmad. “Unveiling the Incidence of Interfirm Collaboration: Evidence from Research and Development Companies in Malaysia”. Gadjah Mada International Journal of Business, Vol. 19, no. 2, Aug. 2017, pp. 123-44, https://jurnal.ugm.ac.id/v3/gamaijb/article/view/15588.