Nick Letzepis Albert Guillen i Fabregas Outage probability of the Gaussian MIMO free-space optical channel with PPM. 3682-3690 2009 57 IEEE Trans. Commun. 12 https://doi.org/10.1109/TCOMM.2009.12.080308 https://www.wikidata.org/entity/Q63957474 db/journals/tcom/tcom57.html#LetzepisF09a