Iowa Testing Programs, I. C., & Forsyth, R. A. (1990). The NAEP Proficiency Scales: Do They Yield Valid Criterion-Referenced Interpretations? Iowa Testing Programs Occasional Papers Number 35, May 1990.
Παραπομπή σε μορφή Chicago (17η εκδ.)Iowa Testing Programs, Iowa City., και Robert A. Forsyth. The NAEP Proficiency Scales: Do They Yield Valid Criterion-Referenced Interpretations? Iowa Testing Programs Occasional Papers Number 35, May 1990. 1990.
Παραπομπή σε μορφή MLA (9th εκδ.)Iowa Testing Programs, Iowa City., και Robert A. Forsyth. The NAEP Proficiency Scales: Do They Yield Valid Criterion-Referenced Interpretations? Iowa Testing Programs Occasional Papers Number 35, May 1990. 1990.
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