To know of

Know \Know\, v. i.
   1. To have knowledge; to have a clear and certain perception;
      to possess wisdom, instruction, or information; -- often
      with of.
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            Israel doth not know, my people doth not consider.
                                                  --Is. i. 3.
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            If any man will do his will, he shall know of the
            doctrine, whether it be of God, or whether I speak
            of myself.                            --John vii.
                                                  17.
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            The peasant folklore of Europe still knows of
            willows that bleed and weep and speak when hewn.
                                                  --Tylor.
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   2. To be assured; to feel confident.
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   {To know of}, to ask, to inquire. [Obs.] " Know of your
      youth, examine well your blood." --Shak.
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