And if you really cannot get ahold of an ad-free one, and Amazon for some stranger reason doesn't do as they normally do for non-US customers and remove them for free, then they will certainly remove the ads for $20 USD which is the amount by which the ad-supported one was discounted by anyway.
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In addition to the excellent information already given by Doitsu, you might want to take a look at the "Dictionary FAQ" sticky in this subforum, which includes links to guides for creating your own dictionary, and sources for stardict dictionaries to convert... as well as some free dictionaries already uploaded here on MobileRead and elsewhere on the internet.