The combination of two obstruent consonants which are different only with regard to their belonging to different ‘Lokalisierungsreihen’ (e.g. pt, xs, sf), occurs only in languages in which other combinations of obstruent consonants are also possible (e.g. sp, tr, kl, rs).
Standardized
IF clusters of obstruent consonants which are different only with regard to their belonging to different ‘Lokalisierungsreihen’ (e.g. sp, tr, kl, rs) are possible, THEN clusters of two obstruent consonants (e.g. pt, xs, sf) are also possible.
