Meyerhoff (2000b) is a detailed discussion of the distribution of null and pronominal subjects. All subjects may be expressed overtly or may be omitted. 1st and 2nd person subjects favour overt realization of pronoun subject. 3rd subjects favour null. Oli and i (glossed as agreement in this dataset) partially identify the person and number of subjects. They are conventionally written as separate words, but are clearly preverbal clitics (no intervening adverbs possible, for instance).
Source: Meyerhoff nd