Elhousseyn, Benguettaia, and Bouhoreira Abbas. “The Role of Research and Development in Increasing the Competitive Performance of Petroleum Companies: A Case Study of Royal Dutch Shell PLC”. The International Tax Journal, vol. 52, no. 5, Oct. 2025, pp. 2545-56, https://internationaltaxjournal.online/index.php/itj/article/view/264.