The Tibetan idea of a tulpa

Everybody says this started in Tibetan Buddhism, but I can't seem to find much credible information on the Tibetan concept of a tulpa. The Wikipedia article seems to cite mostly secondary or questionable sources when referencing the phenomenon of tulpae as thoughtform entities.

The closest I can find to first-hand sources are some passages by Alexandra David-Néel. It's starting to seem to me that everything else relating to Tibetan tulpae (as conjured entities) might be based on her accounts.

It's worth noting that in her descriptions a tulpa is visible to others, can be sent to fulfill missions, and may become rebellious to the point of killing their creators. She notes that some Tibetans disagree on their nature, and think of them as an apparition and a case of suggestion, but talks about making her own tulpa that was visible to others. She also says, "the practice is considered fraught with danger for any one who has not reached a high mental and spiritual degree of enlightenment and is not fully aware of the nature of the psychic forces at work in the process." All this makes it sound more like a golem than a sentient imaginary friend.

So anyway:

1. Given the descriptions, should this Tibetan stuff even be considered the same as what's being discussed in these forums?

2. Does anyone know of some good material on the Tibetan conception of tulpae? Modern Buddhists talking about this would be the ideal.