Follow up to a question answered previously. The question is: "Is a Noahide allowed to work on Shabbat?"
The answer is:A: Yes, he is allowed, unless when he declared to a Beit Din that he accepts the Noahide laws he also took on a specific obligation to observe the laws of Shabbat. But this is very rare (see Be'er Halacha, in Orach Chaim 304).
What is Be'er Halacha, Orach Chaim 304?
Where can I find it?