I grew up with a Concise Oxford Dictionary as the arbitrator of the English language, that Mum had brought over from England. I was very pleased to find a later edition, in a book shop in Sweden so that I could have my own copy when I moved away to university. I keep thinking of getting a subscription to the on-line OED, but have never got as far as finding out how much it would cost... Plus there is something much more satisfactory about looking things up in a physical book!