\input zb-basic \input zb-ioport \iteman{io-port 06083584} \itemau{\v{C}a\v{c}i\'c, Vedran; Vukovi\'c, Mladen} \itemti{A note on normal forms for the closed fragment of system IL.} \itemso{Math. Commun. 17, No. 1, 195-204 (2012).} \itemab The paper is devoted to the interpretability logic IL, in particular to the open problem of the normal form for the closed fragment of IL. Some cases where the modal operator $\vartriangleright$ can be eliminated are given, and a formula from which it is impossible to eliminate it is indicated. \itemrv{Roman Murawski (Pozna\'n)} \itemcc{} \itemut{modal logic; interpretability logic; normal form} \itemli{http://hrcak.srce.hr/index.php?show=clanak&id\_clanak\_jezik=123527&lang=en} \end