1. Biblehub. [online] https://biblehub.com.
2. Catholic Herald. Martyrs and tomorrow’s Church. Catholic Herald. 2018. Available from: https://catholicherald.co.uk/magazine/martyrs-and-tomorrows-church/.
3. Catholic Herald. Pope Francis: Invite God to dwell in your heart this Christmas. Catholic Herald. 2018. Available from: https://catholicherald.co.uk/news/2018/12/24/pope-francis-invite-god-to-dwell-in-your-heart-this-christmas/.
4. Central Office of Church Statistics of the Secretariat of State. The Pontifical Yearbook 2017 and the Annuarium Statisticum Ecclesiae 2015. Summary of Bulletin. Holy See Press Office. 2017. Available from: http://press.vatican.va/content/salastampa/en/bollettino/pubblico/2017/04/06/170406e.html.
5. Greguš, J. Prolegomena to any future discussions on overpopulation. Praha, 2017, p. 6–8. In press 2019.
6. Guillebaud, J. How do contraceptives work? Ecotimecapsule. 2018. Available from: http://www.ecotimecapsule.com/pagecontents/pdfs/contraception/article4a.pdf.
7. Guillebaud, J. Is implantation the biological event which completes conception, and so separates conception from induced abortion? Ecotimecapsule. 2018. Available from: http://www.ecotimecapsule.com/pagecontents/pdfs/contraception/article3a.pdf.
8. Guillebaud, J. Perfect storm. Ecotimecapsule. 2018. Available from: http://www.ecotimecapsule.com/pagecontents/pdfs/perfect-storm.pdf.
9. Meyendorff, J. Marriage: An orthodox perspective. New York: St Vladimir‘s Seminary Press, Crestwood, 2000. p. 58–63.
10. Pontifical Council for the Family. Vademecum for Confessors Concerning Some Aspects of the Morality of Conjugal Life. Vatican: Libreria Vatican. 1997. Available from: http://www.vatican.va/roman_curia/pontifical_councils/family/documents/rc_pc_family_doc_12021997_vademecum_en.html.
11. Pope Paul VI. Encyclical Letter Humanae Vitae. Vatican: Libreria Editrice Vaticana. 1968. Available from: http://w2.vatican.va/content/paul-vi/en/encyclicals/documents/hf_p-vi_enc_25071968_humanae-vitae.html.
12. Pope Francis. Post-Synodal Apostolic Exhortation Amoris Laetitia. Vatican: Libreria Editrice Vaticana. 2016. Available from: https://w2.vatican.va/content/francesco/en/apost_exhortations/documents/papa-francesco_esortazione-ap_20160319_amoris-laetitia.html.
13. Public Broadcasting Service. People & Events: Dr. John Rock. PBS. 2018. Available from: http://www.pbs.org/wgbh/amex/pill/peopleevents/p_rock.html.