Longitudinal structure function FL of proton from Regge-like behaviour of gluon distribution function up to next-to-next-to-leading order at small-xNomita Baruah, Mrinal Kumar Das and Jayanta Kumar SarmaEur. Phys. J. Plus, 129 10 (2014) 229DOI: https://doi.org/10.1140/epjp/i2014-14229-5