Is there an authoritative reference for the stroke order of simplifed characters? It seems various people often have various ways to write the same characters. For instance, I have seen the radical "忄" being written in three different ways (left, middle, right; left, right, middle; and middle, left, right) which is a lot for such a small radical. Chinese teachers sometime don't even agree on what should be the correct stroke order.

So is there any authoritative source on what the correct stroke order for a character should be? Perhaps some book published by the government?
You can reference 《现代汉语通用字笔顺规范》 published by the Ministry of Education of PRC, which includes the stroke order of over 7000 daily used simplified Chinese characters.

If you want to find some traditional Chinese stroke order resources, check this