In theory, a buyer agent only gets a commission if he "procured" the transaction that is, if he took you to the house on your first visit or supplied you with the information or advice that got you to the door.

WSJ: Open House Etiquette

According to the conspiracy theory Strassmeir was an "agent provocateur", not only observing the activities of the far right but also encouraging them to do something illegal.

BBC: Q&A: What really happened

In market theory the "selfishness" of the economic agent - in this case the GP practice - drives the efficiency of the system by forcing other economic agents to compete to provide the most efficient service.

BBC: Health Bill: Where's the strategic argument?

And our legal theory was that the Sundial was a public forum for student expression, and that Rawitch, as an agent of the state, was prohibited by the Constitution from either censoring its content or exacting punishment after the fact.

WSJ: Best of the Web Today: See You in the Funny Papers