Please use these 2 articles for references

Wheaton AG, Jones SE, Cooper AC, Croft JB. Short Sleep Duration Among Middle School and High School Students United States, 2015. MMWR Morb Mortal Wkly Rep 2018;67:8590. DOI: http://dx.doi.org/10.15585/mmwr.mm6703a1

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4824552/pdf/nihms746414.pdf