Optical monitoring of BL Lac object S5 0716+714 and FSRQ 3C 273 from 2000 to 2014 Yu-Hai Yuan, Jun-hui Fan, Jun Tao, Bo-Chen Qian, Denise Costantin, Hu-Bing Xiao, Zhi-Yuan Pei and Chao Lin A&A, 605 (2017) A43 Published online: 06 September 2017 DOI: 10.1051/0004-6361/201630338