- Thesaurus (in Bulgarian) (Sofia University);
- Stanford Encyclopedia of Philosophy (Stanford University);
- Internet Encyclopedia of Philosophy;
- Thesaurus Linguae Maximi Confessoris (Sofia University);
- Thesaurus Theologiae Maximi Confessoris (Sofia University);
- Электронная Философская Энциклопедия (Institute of Philosophy, RAS);
- Jewish Encyclopedia;
- Catholic Encyclopedia;
- Православная Энциклопедия;
- Encyclopædia Iranica;
- Yongle Encyclopedia;
