<https://www.berpendidikan.com/tag/pengertian-definisi-operasional-menurut-sugiyono-2015#webpage>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://www.berpendidikan.com/tag/pengertian-definisi-operasional-menurut-sugiyono-2015>