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Masu, Alberto (19 January 2013). "Nainggolan trequartista dietro a Sau-Ibarbo" [Nainggolan trequartista behind Sau-Ibarbo]. La Gazzetta dello Sport (in Italian). Retrieved 22 March 2017.
"Welkom op de Bosuil, Radja Nainggolan" [Welcome to the Bosuil, Radja Nainggolan] (Press release) (in Dutch). Royal Antwerp. 14 August 2021. Retrieved 15 August 2021.
Casati, Fabio (7 January 2014). "5 cose da sapere su Radja Nainggolan" [5 things you should know about Radja Nainggolan] (in Italian). Squer. Archived from the original on 9 January 2014. Retrieved 8 January 2014.
Schirru, Niccolò (19 October 2010). "Grave lutto per Nainggolan" [Serious mourning for Nainggolan] (in Italian). Tutto Cagliari. Retrieved 8 January 2014.
Piredda, Claudio (27 January 2010). "Le prime dichiarazioni di Nainggolan" [Nainggolan's first statements] (in Italian). Tutto Cagliari. Retrieved 22 March 2017.
Adriansah, Oleh (16 June 2013). "Radja Nainggolan diincar klub besar Eropa" [Radja Nainggolan drafted by big European club] (in Indonesian). Ganlob. Archived from the original on 8 January 2014. Retrieved 8 January 2014.
Casati, Fabio (7 January 2014). "5 cose da sapere su Radja Nainggolan" [5 things you should know about Radja Nainggolan] (in Italian). Squer. Archived from the original on 9 January 2014. Retrieved 8 January 2014.