Checking the variability of the gravitational constant with binary   pulsars
  The most precise measurements are done at present by timing of radiopulsars in binary systems with two neutron stars. The timing measurements of the Taylor-Hulse pulsar B1913+16 gave the most precise results on testing of general relativity (GR), finding implicit proof of existence of gravitational waves. We show that available results of existing measurements, obtained to the year 1993, in combination with the results of the Mariner 10 in (1992), give the boundaries for the variation of the gravitational constant ${\dot G}/{G}$ inside the limits $(-0.6 \div +2)\cdot 10^{-12}$ year{$^{-1}$}. 
G.S. Bisnovatyi-Kogan