Here is the link for the article on page ONE: https://kidshealth.org/en/kids/heart.html
Here is the link for the article on page TWO: https://kidshealth.org/en/kids/work-it-out.html
Here is the link for the article on page THREE: http://www.cyh.com/HealthTopics/HealthTopicDetailsKids.aspx?p=335&np=285&id=1467
Here is the link for the activity on page FOUR: https://www.healthchecksystems.com/heart.asp