How to find ISSN number of IEEE Sponsored (or IEEE related) Events?

My University of Technology requires me to limit my research paper publications to certain (what they refer to as level 1 or 2 venues), which are simply based on ISSN numbers. How do I find out the ISSN numbers for IEEE Sponsored events, such as in Croatia (Europe), who don't provide any ISSN numbers and provide no contact links? Here is the IEEE related conference URL: http://iwcmc.org/2015/? I know that there is a text description of IEEE sponsorship, but there is no ISSN number. Also, I would like to make sure, that based on an ISSN number, Croatia web pages are valid (which is difficult when they conceal contact information). I'm hoping that even if Croatia is non-responsive that IEEE has some master web page, which I can use to verify so called, alleged but not verified, "IEEE Sponsored Events". Thanks so much!!!