Originally thought to be the same as Brachycephalic Airway Syndrome (), current thinking is that NTUAS is different. Documentation of the problem in Norwich terriers is in reference . A grading scheme for the Norwich upper airway was proposed in 2009 in reference ; unfortunately this grading is only done in Switzerland. A study at Michigan State under Dr Bryden Stanley is currently underway to reproduce and extend this work. Currently the only scientific guidance breeders have is given in references [3| and , although this is not widely believed to be relevant to NTUAS.
Updates on Dr. Stanley's research are available. See also this web site, which includes a link to the 2018 NTUAS Owner Survey.
Last updated 20180823.
 Das Obere Luftweg-Syndrom beim Norwich-Terrier: Beschreibung der Erkrankung und der Untersuchungsmethoden, sowie Entwicklung und Evaluierung eines zuchthygienisch nutzbaren Scoring-Schemas., Martina Ruchti, 2009
 Proposal for a new radiological index to determine skull conformation in the dog, D.A.Koch, et al., Schweiz Arch Tierheilkd, 154(5):217-20, May 2012.
 Upper Airway Obstruction in Norwich Terriers: 16 Cases, L.R. Johnson, et al., Journal of Veterinary Internal Medicine, Volume 27 Issue 6, pp. 1409-1415, 30 Sep 2013.
 Comparative investigations on the upper respiratory tract in Norwich terriers, brachycephalic and mesaticephalic dogs, D.A.Koch, et al., Schweiz Arch Tierheilkd, 156(3):119-24, Mar 2014.