On the alpha activity of natural tungsten isotopes
  The indication for the alpha decay of 180-W with a half-life T1/2=1.1+0.8-0.4(stat)+-0.3(syst)x10^18 yr has been observed for the first time with the help of the super-low background 116-CdWO_4 crystal scintillators. In conservative approach the lower limit on half-life of 180-W has been established as T1/2>0.7x10^18 yr at 90% C.L. Besides, new T1/2 bounds were set for alpha decay of 182-W, 183-W, 184-W and 186-W at the level of 10^20 yr. 
F. A. Danevich, A. Sh. Georgadze, V. V. Kobychev, S. S. Nagorny, A. S.   Nikolaiko, O. A. Ponkratenko, V. I. Tretyak, S. Yu....