In terms of topics, there were more references on access compared to volunteering, although some studies integrated both within broader discussions of ethnicity and environmental engagement.
O ran pynciau, roedd mwy o gyfeiriadau at fynediad o gymharu â gwirfoddoli, er bod rhai astudiaethau yn integreiddio'r ddau mewn trafodaethau ehangach am ethnigrwydd ac ymgysylltu amgylcheddol.