=IF(ISTEXT(Sheet1!A2), Sheet1!A2, "")

= IFERROR( INDEX(INDIRECT("EsZkouska");
  SMALL(IF((INDEX(INDIRECT("EsZkouska");;1‌​;1)="ČSN721180")*(INDEX(INDIRECT("EsZkouska");;9;1)="RC_P_B");
  ROW(INDIRECT"EsZkouska"))-MIN(ROW(INDIRECT("EsZkouska")))+1;"");1);17;1);"")

{=IF(RC_P_B<>""; RC_P_B;"---")}