Tamura, K., R. Goto, N. Yamada, K. Nakatsuka, K. Uchida, K. Horibe, K. Saeki, H. Encho, M. Tezuka, M. Mukaijo, and R. Ono. “Relationship Between Peer Group Size and Active Outdoor Play in Children Aged 9-12 Years: Oral Presentation A2.1”. The Health & Fitness Journal of Canada, vol. 14, no. 3, Sept. 2021, doi:10.14288/hfjc.v14i3.381.