Difficult Airway ASA Guidelines 2013
Practice guidelines for management of the difficult airway: an updated report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway.
Anesthesiology 2013
http://www.ncbi.nlm.nih.gov/pubmed/23364566
https://doi.org/10.1097/ALN.0b013e31827773b2