  This talk is dedicated to the memory of Paco Yndurain, the original speaker
in the conference. After a short account of his scientific career, we briefly
review our ongoing collaboration to determine precisely the $\pi\pi$ scattering
amplitude including the most recent data by means of Forward Dispersion
Relations and Roy Equations. A remarkable improvement in precision over the
intermediate energy region is obtained by using once-subtracted Roy Equations
in addition to the standard twice-subtracted ones.
