Diacritics in the Vietnamese name "Nguyen"

The Vietnamese name that is commonly written as "Nguyen" in English texts apparently needs to have a circumflex on the "e" in the correct spelling. But is this all? From what seem to be attempts at writing Vietnamese names correctly, I've found e.g. "Nguyen Le" (the musician) with circumflexes on the "e" letters but no other circumflexes, whereas "Nguyen van Thieu" has several diacritics, including both a circumflex and a tilde on the "e" of "Nguyen".

The article http://en.wikipedia.org/wiki/Nguyen says that Nguyen is a very common name and writes it first with the two diacritics, then with none. I can understand the practical reasons behind this, as well as reasons for using the circumflex alone (since "e" with circumflex belongs to the ISO Latin 1 set, so it is essentially easier to write in most situations than "e" with both diacritics).

But is it all about a single name, which should have two diacritics but is often written without one or both? Or is it about two names, or forms of a name? Finally, what might be the correct spelling of "Nguyen Le"? (What diacritics does "Le" carry?)

Yucca
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