Add icon for interface.
@string{JFP="J. Functional Programming"}
@article{MuellerNvOS99,
author=
{Olaf M{\"u}ller and Tobias Nipkow and Oheimb, David von and Oskar Slotosch},
title={{HOLCF = HOL + LCF}},journal=JFP,year=1999,volume=9,pages={191--223}}