[...] we may speak of 'additive suprafixes' (the Ngbaka data) [p. 63 In this series of Ngbaka words the segmental phonemes constitute the morphemes which 'carry' the meanings 'to put,' 'to clean,' 'to pull,' and so on. The differences of tones indicated four principal tense-aspect contrasts.]
- Nida (1949), Pag. 69