As a result, constitutions are no longer a very useful guide to where power lies.

I thought that geography might prove a useful guide.

Now they have suggested that their simulation of a wormhole would be a useful guide for teaching students about the mechanics of general relativity.

Used with care, they can provide a useful guide, source of inspiration and validation of your existing fund choices.

The following tables are a useful guide to which universities do the main subjects best, covering teaching quality, research prowess and graduate prospects.