All the audio recordings have been made by nativespeakers, some of whom like Alfred "Bud" Lane are among the last fluent individuals in their native tongues.
The number of areas of Wales where Welsh is the majority language - in north and west Wales - is still reducing, fuelling fears that the language may lose its capacity to produce new nativespeakers.
They studied bilingual programs in the Houston Independent School District and found that native-Spanish speakers were at or above grade level in English and Spanish in first grade through fifth grade.