1. British English CHILDES Corpora . < http://childes.psy.cmu.edu/data/ > Eng-UK-MOR/ .
2. British English CHILDES Corpora ( manuals ). < http://childes.psy.cmu.edu/manuals/ >
3. OED online . < http://www.oed.com >
4. Oh and ah in English conversation;Aijmer,1987