Pronunication of 昭

Hello,

I always thought 昭 could be pronounced as ciu1 or ziu1. When I looked up the character, Cantodict only has the first pronunciation listed. The compound words have examples with both pronunciations. Also, CUHK's dictionary lists both pronunciations as valid: [humanum.arts.cuhk.edu.hk] Could someone please look into this?

Thanks!