Subject to special provisions, the following are liable to registration duties:
1° When they do not give rise to the merged formality, the deeds referred to in 1 of article 635 ;
2° The acts referred to in 1°, 5°, 7° and 7° bis of 2 of article 635 and in article 636 and generally all deeds voluntarily submitted to the formality of registration;
3° Transfers resulting from oral agreements referred to in articles 638,639 and 640;
4° Transfers by death.