  Photometric observations in V and I bands of six eclipsing binaries at the
lower limit of the orbital periods of W UMa stars are presented. Three of them
are newly discovered eclipsing systems. The light curve solutions revealed that
all short-period targets were contact or overcontact binaries and added new six
binaries to the family of short-period systems with estimated parameters. Four
binaries have equal in size components and mass ratio near 1. The phase
variability of the V-I colors of all targets may be explained by lower
temperatures of their back surfaces than those of their side surfaces. Five
systems revealed O'Connell effect that was reproduced by cool spots on the side
surfaces of their primary components. The light curves of V1067 Her in 2011 and
2012 were fitted by diametrically opposite spots. The applying of the criteria
for subdivision of the W UMa stars to our targets led to ambiguous results.
