Period variations of flares from TVLM 513. The filled square, triangle, and circles represent period measurements based on the data from Hallinan et al. (2009), Doyle et al. (2010), and the Arecibo measurements discussed in this paper, respectively. The horizontal, dashed line marks the best-fit period derived from the timing model of the entire set of arrival time measurements made between 2006 and 2013.