當當= China e-bookshop
idxx = a bookshop in Mkk and CWB selling books from China and also Engl books from Engl publishers.
You can find the real names / address / tel no / websites under the topic about Chin Bookshops ("好書分享"置頂).
Since their names appear very often in FXPC and GloriaChung's topics, I (and most BKmums) usually use xxx instead of real name of bookshop, so that we are not accused of promoting business here.
I know what is "當當"; however, I am so stupid that I cannot find the information of "idxx" from the topics. Is it possible for you to PM the details to me? Thanks!