S i j  P H Y   = − ∑ k = 1  229   log ⁡ [ P ( x i k   , x j k   ) ]   .       ( 1 )    MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8akY=wiFfYdH8Gipec8Eeeu0xXdbba9frFj0=OqFfea0dXdd9vqai=hGuQ8kuc9pgc9s8qqaq=dirpe0xb9q8qiLsFr0=vr0=vr0dc8meaabaqaciaacaGaaeqabaqabeGadaaakeaacqWGtbWudaqhaaWcbaGaemyAaKMaemOAaOgabaGaemiuaaLaemisaGKaemywaKfaaOGaeyypa0JaeyOeI0YaaabCaeaacyGGSbaBcqGGVbWBcqGGNbWzcqGGBbWwcqWGqbaucqGGOaakcqWG4baEdaWgaaWcbaGaemyAaKMaem4AaSgabeaakiabcYcaSiabdIha4naaBaaaleaacqWGQbGAcqWGRbWAaeqaaOGaeiykaKIaeiyxa0faleaacqWGRbWAcqGH9aqpcqaIXaqmaeaacqaIYaGmcqaIYaGmcqaI5aqoa0GaeyyeIuoakiabc6caUiaaxMaacaWLjaWaaeWaaeaacqaIXaqmaiaawIcacaGLPaaaaaa@568D@