... data

Based on data obtained at: the European Southern Observatory, La Silla, Chile, the Télescope Bernard Lyot, Calar Alto Observatory, Las Campanas Observatory. Also based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Institute.

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...

Figures 1-35 are only available in electronic form at the http://www.edpsciences.org

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... bar

We mean bar = primary bar; when considering secondary bars, it will be clearly stated.

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... galaxies

In a strict sense, they are weakly interacting systems, since we don't take into account the possibility of being surrounded by dwarf galaxies or HI clouds.

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... IRAF

IRAF is the Image Analysis and Reduction Facility made available to the astronomical community by the National Optical Astronomy Observatories, which are operated by the Association of Universities for Research in Astronomy (AURA), Inc., under contract with the U.S. National Science Foundation.

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... bars

We note that all the elongated central structures we call secondary bars could be either bars or elongated rings or disks; kinematical data will help to discriminate among them.

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