Are indefinite descriptions ambiguous?

I have benefited greatly from discussing the issues addressed in this paper with Michael Liston, John Vickers and Mark Wilson.     

Relation between musical aptitude and intelligence among mentally retarded, advantaged, and disadvantaged subjects

The purpose of this study was to investigate differences in scores of 59 mentally retarded adults (mild, moderate, severe, or profound), 133 advantaged, and 130 disadvantaged (low income) children in Grades 1, 2, 3 on the Primary Measures of Music Audiation. Test-retest reliabilities for the Tonal and Rhythm subtests were .81 and .86, respectively, for the retarded group. Analysis of variance indicated that the mildly retarded children performed significantly better than other groups of retarded children on these two tests. 2 x 3 analyses of variance indicated that third graders from both advantaged and disadvantaged groups performed significantly better than the first or second graders on both subtests and that advantaged children performed significantly better than the disadvantaged. However, disadvantaged children made greater gains, especially for third graders, than the advantaged.     

Listeriosis of the central nervous system in children beyond the neonatal period

Observations on three children with neurolisteriosis (one case of meningitis, two cases of meningoencephalitis, each Serovar 4 b), show that even after the neonatal period, listeriosis must not be ignored in the process of diagnosis and therapy. It is the bacteriological examination of the cerebrospinal fluid, together with the blood culture, and not clinical symptoms and serology that guarantee a timely diagnosis and therapy (ampicillin and gentamicin).