Behavioral Variation in Gorillas: Evidence of Potential Cultural Traits. oleh Martha M Robbins, Chieko Ando, Katherine A Fawcett, Cyril C Grueter, Daniela Hedwig, Yuji Iwata, Jessica L Lodwick, Shelly Masi, Roberta Salmi, Tara S Stoinski, Angelique Todd, Veronica Vercellio, Juichi Yamagiwa