“Identify the Differences Between Ordinary and Barred Spiral Galaxies, NGC 2649 and NGC 4662 for Examples”. Iraqi Journal of Science 65, no. 10(SI) (November 15, 2024): 6197–6204. Accessed December 18, 2024. https://ijs.uobaghdad.edu.iq/index.php/eijs/article/view/12525.