Familienverband der Freiherren von Quast (25 October 2015). "Who is entitled to the prefix of 'Sir'?". Nobiliary law – Adelsrecht – Droit nobiliaire. Archived from the original on 1 April 2019. Retrieved 6 December 2017.
"Republic Act No. 646". Official Gazette of the Republic of the Philippines. 14 June 1951. Archived from the original on 6 December 2017. Retrieved 6 December 2017.
Familienverband der Freiherren von Quast (25 October 2015). "Who is entitled to the prefix of 'Sir'?". Nobiliary law – Adelsrecht – Droit nobiliaire. Archived from the original on 1 April 2019. Retrieved 6 December 2017.
"Republic Act No. 646". Official Gazette of the Republic of the Philippines. 14 June 1951. Archived from the original on 6 December 2017. Retrieved 6 December 2017.