1. Abd, M., Majed, S., Zharkova, V.: 2010 Automated Classification of Sunspot Groups with Support Vector Machines. ISBN 978-90-481-9150-5. DOI.
2. Baldi, P., Hornik, K.: 1989, Neural networks and principal component analysis: Learning from examples without local minima. Neural Netw. 2, 53. DOI.
3. Bao, X., Lucas, J., Sachdeva, S., Grosse, R.B.: 2020, Regularized linear autoencoders recover the principal components, eventually. In: Larochelle, H., Ranzato, M., Hadsell, R., Balcan, M.F., Lin, H. (eds.) Advances in Neural Information Processing Systems 33, Curran Associates, Red Hook, 6971.
4. Chen, Y., Manchester, W.B., Hero, A.O., Toth, G., DuFumier, B., Zhou, T., Wang, X., Zhu, H., Sun, Z., Gombosi, T.I.: 2019, Identifying solar flare precursors using time series of SDO/HMI images and SHARP parameters. Space Weather 17, 1404. DOI.
5. Colak, T., Qahwaji, R.: 2008, Automated McIntosh-based classification of sunspot groups using MDI images. Solar Phys. 248, 277. DOI. ADS.