D'a, ì. A., Pinto, C., Del Santo, M., Pintore, F., Soria, R., Robba, A., …Walton, D. (2021). The chameleon on the branches: spectral state transition and dips in NGC 247 ULX-1. Monthly Notices of the Royal Astronomical Society, 507(4), 5567-5579. https://doi.org/10.1093/mnras/stab2427