AskOxford.com is the Web site of the Oxford University Press:
Oxford University Press is a department of the University of Oxford. It furthers the University’s objective of excellence in research, scholarship, and education in its worldwide publishing. The preparation of dictionaries, of all types and for all ages, has been a central part of its activities for more than 100 years.
The Web site offers many different dictionaries and grammar and punctuation tools. It’s extremely helpful, whether for legal writing or other types of writing.