Title Twin signed domination numbers in directed graphs Type of Research Article Keywords twin signed dominating function, twin signed domina-tion number, directed graph Abstract twin signed dominating function, twin signed domina-tion number, directed graph Researchers maryam atapour (First Researcher)، Sepideh Norouzian (Second Researcher)، Seyed Mahmoud Sheikholeslami Kavkani (Third Researcher)، Lutz Volkmann (Fourth Researcher)