The TDK reference article from the English Wikipedia on 24-Apr-2004
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TDK

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TDK is a company that manufactures electronic materials, electronic components, and recording and data-storage media. It was founded in Japan in 1935 to manufacture ferrite, which had been recently invented by Yogoro Kato.

Also, TDK (Turk Dil Kurumu) is the initialism of Turkish Language Association.