A. K. . Ahmed, A. S. . Taha, and A. A. . Kadhem, “Identify the differences between ordinary and barred spiral galaxies, NGC 2649 and NGC 4662 for examples”, Iraqi Journal of Science, vol. 65, no. 10(SI), pp. 6197–6204, Nov. 2024, doi: 10.24996/ijs.2024.65.10(SI).25.