Hong Kong's richest tycoon Li Ka-shing said Friday he is retiring as chairman of the conglomerate CK Hutchison Holdings, effective in May.With wealth of about US$34.9 billion, Li, 89, once dubbed "superman" for his rags-to-riches story, ranked 23rd in the latest Forbes World's Billionaires list."Having been working since I was 12, still being in good physical shape and having a clear head, I feel grateful," Li saidduring the company's results announcement.His elder son Victor will take the helm while Li will remain an adviser to the company.The Cheung Kong group's businesses span ports, uti…READ FULL ARTICLE