Bybee et al. (1994: 54): "Past indicates a situation which occurred before the moment of speech. In a given use of a particular gram, the meaning label past may co-occur with one or more of a range of other meaning labels, such as imperfective, habitual, and progressive, among others. In this chapter we consider only grams which have past as the sole meaning label of a use, past perfectives, and those that signal remoteness distinctions in the past. A simple past resembles a perfective in that it is the tense of narration of sequences of past events."