Laasonen, E. and Laasonen, L. 2000. Habitual differences of <i>Phyllonorycter salictella</i> (Zeller, 1846 ) and <i>P. heringiella</i> ( Grönlien, 1932) (Lepidoptera: Gracillariidae) in two Finnish materials; a problem pair. Entomologica Fennica. 11, 3 (Sep. 2000), 175–181. DOI:https://doi.org/10.33338/ef.84063.