Book: Describing Language: Form and Function
Chapter: Chapter 2: Directions from Structuralism 
This paper shows the variation, the potentiality, the synchronic oscillation, of the sign structuralism. Following Firth in rejecting Saussure’s langue/parôle dichotomy, Hasan argues that potentiality in language is always limited by who we are, how others see us, what rights we enjoy, what obligations we carry. In other words, the potentiality of the sign is actualized within a social context.