Sales of cultural merchandise from South Korea's national museums topped 20 billion won ($13 million) for the first time in the first half of this year, driven by the global popularity of Korean culture, sources in the cultural sector said Monday. The National Museum Foundation of Korea's official merchandise brand Mu:ds recorded about 21.8 billion won in sales from January to June, up roughly 90 percent from 11.48 billion won a year earlier, according to the sources. Mu:ds -- a portmanteau of "