Onodera, S.; Sofue, Y.; Koda, J.; Nakanishi, H.; Kohno, K. (2002). "CO (J=1-0) Observations of the Non-Barred Seyfert 2 Galaxy NGC 4501". Dalam Ikeuchi, S.; Hearnshaw, J.; Hanawa, T. Proceedings of the IAU 8th Asian-Pacific Regional Meeting. Bibcode:2002aprm.conf..199O.