Regional density of cardiologists and rates of mortality for acute myocardial infarction and heart failure
Circulation: Cardiovascular Quality and Outcomes
http://www.ncbi.nlm.nih.gov/pubmed/?term=Regional%20density%20of%20cardiologists%20and%20rates%20of%20mortality%20for%20acute%20myocardial%20infarction%20and%20heart%20failure.