Simon Lind Kappel Preben Kidmose Study of impedance spectra for dry and wet EarEEG electrodes. 3161-3164 2015 EMBC https://doi.org/10.1109/EMBC.2015.7319063 https://www.wikidata.org/entity/Q51574224 conf/embc/2015 db/conf/embc/embc2015.html#KappelK15