Study of the relative difficulty of judging types of articulatory productions, 190 - 01 - 04 - LD1017 .C8133 1969 M31, Volume: Archives LD1017 .C8133 1969 M31; Volume: Carlson Library Level A Main Quarto Collection LB3454 .M3. Clarion University Archives. http://buoy1.klnpa.org/repositories/2/resources/292 Accessed April 25, 2025.