Thực đơn
Lạc quan Tham khảoThực đơn
Lạc quan Tham khảoLiên quan
Tài liệu tham khảo
WikiPedia: Lạc quan http://www.oxforddictionaries.com/definition/engli... http://www.sciencedirect.com/science/article/pii/S... //pubmed.ncbi.nlm.nih.gov/22153158 //pubmed.ncbi.nlm.nih.gov/26561494 //www.ncbi.nlm.nih.gov/pmc/articles/PMC4637169 //doi.org/10.1016%2Fj.cub.2011.10.030 //doi.org/10.1080%2F17439760.2015.1015155 https://www.youtube.com/watch?v=U9cGdRNMdQQ https://web.archive.org/web/20140606234436/http://...