What is the correct spelling of Paul Erdős's name? I am not quite sure that this question belongs to the math.stackexchange.com. What I am sure is that definitely there are people here who know the answer to my question. On the Internet and in the literature I saw two different types of spelling of the last name of Paul Erdös (together with the wrong one "Erdos"): 1. Erdős 2. Erdös In the former case it is called "long Hungarian umlaut (double acute)" and in the latter "umlaut, trema or dieresis". Hence the question: which choice is the correct one, or maybe they both can be used interchangeably?

The former is the correct spelling, but outside of $\mathrm\LaTeX$ and its `\H` command it's hard to enter, so a lot of people just use umlauts which are easier to type on a keyboard.