In-text: Mayo Health (2014) provided a comprehensive list …., or, if used at the end of the sentence: Early warning signs to look out for … (Mayo Health, 2014). 

Reference list: Mayo Health (2014). “Surviving a heart attack: your early warning signs”. Available from: <http://www.mayohealth.com/i-cms?page=10221>;. [Accessed on 8 May 2015].