• On approximation processes defined by a cosine operator functionKivinukk, Andi; Saksa, Anna; Zeltser, MariaProceedings of the Estonian Academy of Sciences2017 / p. 214-224 https://doi.org/10.3176/proc.2017.2.11 http://www.ester.ee/record=b2355998*est https://artiklid.elnet.ee/record=b2820949*est