de Villiers, Pieter Gideon Retief, and George Marchinkowski. “Sabbath Keeping and Sunday Observance As Spiritual Practice”. Stellenbosch Theological Journal 6, no. 2 (January 22, 2021): 175–200. Accessed October 18, 2025. https://ojs.reformedjournals.co.za/index.php/stj/article/view/2097.