SIMBAD references

The periods of TY and TZ Canes Venatici, both RR Lyrae stars, are studied by means of O-C diagrams. The diagram for TY CVn is definitely not linear but the limited amount of data do not define the functional form. Linear elements approximating the behavior in 1977-1987 are: JD(max) = 2445294.188 + 0.51344266 E. TZ CVn seems to have a constant period, although slightly different from the published value. The new elements are: JD(max) = 2434967.113 + 0.55187911 E.