1. Cricoid pressure impedes placement of the laryngeal mask airway;Asai;British Journal of Anaesthesia,1995
2. Cook T Frerk C (editors) Chapter 19: Aspiration of gastric contents and blood. In: NAP4: 4th National Audit Project of The Royal College of Anaesthetists and The Difficult Airway Society: Major complications of airway management in the United Kingdom [March 2011]. The Royal College of Anaesthetists, 2011 Available from www.rcoa.ac.uk/nap4
3. Deeks J Higgins JPT Altman DG Chapter 9: Analysing data and undertaking meta-analysis. In: Higgins JPT, Green S (editors). Cochrane Handbook for Systematic Reviews of Interventions Version 5.1.0 [updated March 2011]. The Cochrane Collaboration, 2011 Available from www.cochrane-handbook.org
4. Meta-analysis in clinical trials;DerSimonian;Controlled Clinical Trials,1986
5. Bias in meta-analysis detected by a simple, graphical test;Egger;BMJ (Clinical Research Ed.),1997