Add a referenceEdit
We added a statement that seems like common sense — a member of an assembly is a member of an assembly. But what's obvious to you may not be obvious to others. There's a source, an academic book called Politics in a Half Made Society that's perfect for this.
Click "+ add reference". Wikidata allows you to be specific in describing how you are referencing something. In this case we know this fact is stated in Politics in a Half Made Society. We can click in the property box and pick "stated in", and start typing
And we're done.