For the purposes of discussing this feature, the determiner wan(bala) is considered an indefinite article. It is identical to the numeral 'one'. This analysis is not unproblematic, as wan(bala) is not obligatory in indefinite contexts. Sandefur (1979: 104) considers it a marker of indefinite specificity: "There is one determiner, however, that functions somewhat like an article. Wanbala, though most often used as the number 'one', is not infrequently used in the sense of 'a certain'." See Feature 10 "Position of indefinite article in the noun phrase" for additional examples.
Source: Galmurr and Willika 1996
Source: Brennan 1993
Source: Angelo et al. 1998
Source: Hudson 1985: 55