From the testimony of the ancient phonetic treatises of the Vedic age we know that final stops were realized as unreleased 'lenes' like stops in close contact (phenomenon covered by the term 'abhinidhana' - 'incomplete articulation'). For this matter the thesis advocated by R. Gauthiot and A. Meillet of the unreleased character of final Indo-European obstruents needs to be taken into consideration. This concept gains further confirmation in the framework of Trubetzkoy's theory of neutralization and the archiphoneme.
The first to draw the conclusions from this approach for the Indo-European phonological system was O. Szemerényi, who subjected the Latin, Oscan and Germanic material combined with that of Vedic and Avestan to closer scrutiny. Since then the phenomenon in question has gained a wider data-base by including material from Anatolian languages, provided by H. C. Melchert. This evidence allows for the exploration of the phonological relevance of certain manner of articulation features in the Indo-European languages and for an account of the Proto-Indo-European root structure constraint.