Cross Worksheet References in Google Spreadsheets

I was struggling to reference a cell from one sheet of a Google spreadsheet into another sheet. The google spreadsheet help wasn't helpful. The refer to 'cell references' all over but don't mention how to do it.

It's pretty easy. Here is a reference to cell B9 in a worksheet named john
=john!B9

I found that I could also type equals (=) followed by clicking on the john worksheet link and make the referencing by directly clicking.