Não informado. (2020). Progress Report of the Bulgarian National Committee for the International Biological Programme. Bulgarian National Committee for the International Biological Programme.
Παραπομπή σε μορφή Chicago (17η εκδ.)Não informado. Progress Report of the Bulgarian National Committee for the International Biological Programme. Sofia: Bulgarian National Committee for the International Biological Programme, 2020.
Παραπομπή σε μορφή MLA (8th εκδ.)Não informado. Progress Report of the Bulgarian National Committee for the International Biological Programme. Bulgarian National Committee for the International Biological Programme, 2020.
Πρόσοχή: Οι παραπομπές μπορεί να μην είναι 100% ακριβείς.