Factative (unmarked) tense-aspect normally assigns [+past] [+completive] values to unmarked non-stative verbs, and [-past] [-completive] values to unmarked stative verbs. Discourse features, adverbials of time, etc. can assign [-past] and/or [-completive] values to unmarked non-stative verbs and [+past] and/or [+completive] values to unmarked stative verbs.
Source: Faraclas 1996: 188-189
Source: Faraclas 1996: 188-189
Source: Faraclas 1996: 188-189