"Pomagajte uredniku pri izbiri naslovnice. Kliknite na tisto, ki vam je najbolj všeč!"
...as it turns out you just need to click on the link below and then on one of the images (if possible on the one with the geranium pistil, please ;-). If you have installed more than one browser on your computer, it's possible to vote from different browsers, e.g. Firefox, Safari, Opera, Explorer, ...
After successful voting, your cursor will change from a small white hand into a black arrow and in parallel, the current percentage count will be displayed above each image... it currently looks very promising.
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addendum (25th Nov 2009): voting closed with Micronaut in pole-position, looking forward to see this cover printed
Many thanks to all voters !!