<p>I am building apps to make vocabulary acquisition difficult - in a good way: http://vocabulary-journal.com; I can be reached at lerner@vocabulary-journal.com for any related issues.</p>
<p><a href="https://www.oreilly.com/library/view/wtf-whats-the/9780062565723/text/9780062565723_Chapter_13.xhtml" rel="nofollow noreferrer">Knowledge compounds when it is shared.</a><br />
<a href="https://forum.duolingo.com/comment/763796/Lehren-hei%C3%9Ft-lernen" rel="nofollow noreferrer">Lehren heißt zweimal lernen.</a></p>

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Lerner Zhang