I want to add something to what I said in Mandarin phonology with IPA:

It seems both sources, Hànyǔ Pǔtōnghuà Yǔyīn Biànzhèng and Das neue chinesisch-deutsche Wörterbuch, make a mistake on at least two finals. I say mistake though knowing that the depiction chosen depends heavily on your own interpretation of IPA and/or the Standard Mandarin language. I want to explain why.

1. -üan (in yuan, juan, quan, xuan, see Views on initials and finals of Mandarin in Pinyin) is written as [yan], and thus equals -iao [iau] on phone [a], where in fact it is pronounced equal to -ian [iɛn] with [ɛ] (IPA only in source 1). I would thus write it as [yɛn].
2. -iong (yong, jiong, qiong, xiong) is written as [yŋ] and therefor equals -ün [yn] on [y] but in fact it is pronounced equal to -ong [uŋ] so I would write [iuŋ].

Compare to article Pinyin on the English Wikipedia.

I will still stick tightly to the book when implementing the conversion table, but might point out this problem.