Classical Cepheids and the spiral structure of the Milky Way
  We use the currently most complete collection of reliable Cepheid positions
(565 stars) out to ~5 kpc based mostly on our photometric data to outline the
spiral pattern of our Galaxy. We find the pitch-angle to be equal to 9--10
degrees with the most accurate estimate (i=9.5 +/-0.1 degrees) obtained
assuming that the spiral pattern has a four-armed structure, and the solar
phase angle in the spiral pattern to be chi_0 = 121+/-3 degrees. The pattern
speed is found to be Omega_P=25.2+/-0.5km/s/kpc based on a comparison of the
positions of the spiral arms delineated by Cepheids and maser sources and the
age difference between these objects.
