google book is the most useful one
A normal one.
A line graph is most useful for representing how one variable influences another variable.
There is a lot of useful college on-line dictonary and there is not one that is more useful than an other. The one that was voted the best is larousse.
There's really only one kind of gravitational force, and explosions don't create it. Masses do.
Don't believe there is an 'standard' abbreviation. One way to abbreviate -- useful as a kind of informal shorthand --is to eliminate most vowels, something like this:ntrvu
since most people live on one of them, those people probably consider them to be useful
a sat phone
It is one of the most useful tools available.
Granite is one kind of hard rock.
The most rare mighty beans are useful because everyone wants it so you can trade lots of mighty beans for that rare one.
While there are many websites out there that provide good recipes, it does help to know what kind of recipes one is looking for (soups, pastas, etc.). One site that is most useful after answering what kind of recipe you are looking for, is www.allrecipes.com as many users upload their own recipes to share.