I want to know the answer to the following question:
What did Margo McCaffery introduce in 1968?
All the background I'm provided with is that "A definition of pain widely employed in nursing, emphasizing its subjective nature and the importance of believing patient reports, was introduced by Margo McCaffery in 1968: "Pain is whatever the experiencing person says it is, existing whenever he says it does".". Is that enough to answer the question?