British heart foundation
MLA citation: British Heart Foundation. “How Your Heart Works.” British Heart Foundation, Nov. 2024, www.bhf.org.uk/informationsupport/how-a-healthy-heart-works.
Analysis: This site is a legitimate source. Background research shows that british heart foundation is a old non-profit organization that founds heart-related research. A quick WHOSIS lookup also shows that the website's been there since before 2000. This long-living factor proves that it is not likely to be scam. This is further proved when it matches my prior knowledge (from reading, hard to trace) and it does not use strong stress-inducing language.
U.S. national library of medicine
MLA citation: Institute for Quality and Efficiency in Health Care. “How Does the Blood Circulatory System Work?” National Library of Medicine, Institute for Quality and Efficiency in Health Care (IQWiG), 21 Nov. 2023, www.ncbi.nlm.nih.gov/books/NBK279250/.
this website is used for complimentary research. it is definitely safe due to the .gov suffix. It analyzes scientifically.