TCDD, the most toxic member of the family, is used as reference compound, and all other dioxins are assigned a toxic potency relative to TCDD, based on experimental studies.

TCDD在这个家族中毒性最强，被用作参照物，所有其它二恶英均根据实验研究确定相对于TCDD的毒性。

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One drawback was that in the teach-me mode, we didn't see all of the examples of compound kanji words that the reference mode gave us. (A kanji can have different readings and, depending on the character or characters it is combined with, different meanings.) App creator Rory Prior says he is considering adding a vocabulary-training feature to the teach-me mode to address that.

WSJ: Mobile Apps for Foreign Languages