Before I explain why your formula has double square brackets, it's important to understand the difference between direct and ...

Nottingham city centre is the cultural, commercial, financial and historical heart of Nottingham. The centre of the city is usually defined as the Old Market Square – the UK's largest city square.

In the United States, a Black person is 3.73 times more likely to be arrested for marijuana possession than a white person is, despite approximately equal rates of use.