On page kd of Opperlans! Taal -& letterkunde (Querido, 2003), Battus (the pen name of Hugo Brandt Corstius) presents a new way to define a vowel in the Dutch language. He originally presented this argument in the journal Spektator (1972). The following is an adaptation to the English language.
Eckler, A. Ross
"On the Definition of a Vowel,"
Word Ways: Vol. 48
, Article 25.
Available at: http://digitalcommons.butler.edu/wordways/vol48/iss2/25