2. http://hea-www.harvard.edu/vlp_m33_public/tpannuti_aas.pdf
... Wavelength-Dependent Selection Effects in Searches for SNRs in Nearby Galaxies Venn diagram depicts optical, radio and X-ray (Chandra) detections of SNRs in five nearby spiral galaxies (M81, M101, NGC 2403, NGC 4736 and NGC 6946) (Limiting LX ? ...
3. http://sn.sai.msu.ru/~sil/preprints/n80.pdf
... NGC 80 : 11 , , , . , NGC 80 . , - . 1. - , , , , (. NGC 4736 - [1], NGC 7742 - [2] ). , , [3, 4]: , , , , , , , . , ; (NGC 7217 [5]) [6, 7]. , , , , ? , [8]. ...