Johnson, R. Burke.

    Educational research : quantitative, qualitative, and mixed approaches / Burke Johnson, Larry Christensen. 4th ed.

    Los Angeles [etc.] : SAGE, cop. 2012. XXVI, 621 s. : il. ; 26 cm.
    ISBN 978-1-4129-7828-6

   
T.17531        UKD: 303:37]=111