https://jessepearson.net/2015/01/adding-css-classes-wordpress-widget/
Adding CSS classes to a WordPress Widget - Jesse Pearson
Jan 8, 2015 - Let me preface this, this is only if you are creating a widget and not if you just want to add a class to an existing widget, there are plugins that do that....
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https://www.vice.com/sv/contributor/jesse-pearson-jerry-hsu/
Jesse Pearson, Jerry Hsu - VICE
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