Frankly, my own sense of the constructive - ism versus the construction - ism discussion, is that this is a particular moodle-like distinction. In fact, this discussion itself is part of the process of engaging in the social construction of knowledge. A key publication in setting out this idea of the social construction of knowledge is the book: Berger and Luckmann's The Social Construction of Reality (1966). If you want to go to one of the sources of contemporary theorizing on this topic, that would be a good resource. I am not suggesting that it is an easy resource to read, but if you want a seminal work, that would be one.
A more 'quick and dirty' summary -- in the context of collaborative learning -- might be a paper by Arthur Warmoth. I am not suggesting this paper is the definitive source; but it is a source which seems to be substantive and authoritative.
Hope this is of some help.