Chapter 3: Linguistic Sign and the Science of Linguistics 
Describing Language: Form and Function - The Collected Works of Ruqaiya Hasan Vol 5 - Ruqaiya Hasan†
Ruqaiya Hasan† [+]
The appliability of Systemic Functional Linguistics derives from its ability to show how language works in context of situation. This ability arises from the pursuit of a viable conception of the sign such as Saussure’s to its logical end, renders SFL capable of being used to help solve any problem that implicates language in any social activity.