I have read the interesting discussions e.g. [in the comments here](http://esperanto.stackexchange.com/a/1526/503) and concluded that there should be a glide, rather than a glottal stop, in *scienco*, since the *ie* occurs within [a single root](http://www.esperanto-chicago.org/rootsglossary.htm), as opposed to, for example, the *ii* in *sciigo*. Yet I have heard a clear /st͡siʔ'ent͡so/ on Duolingo. I suppose there is some leeway, that's alright. But trying my best at what was meant to be the canonical pronunciation makes me feel better than "it's OK if you keep saying either way". What would the books say about this word?