Is it appropriate to ask authors for their data-sets?

[Linfeng Li]

Hi group, 

I am still working on my data-searching process and I am still stuck with getting access to those data.

After days of searches, I came across a paper which is built on top of the data exactly what I am looking for. I am wondering if it would be appropriate to ask for the data-set from the author deliberately? 

The best I am expecting is to have the author tell me what are his "dozens of studies of state coalitions and governments". He didn't even cited those works in his paper.

My concern is that, by deliberately asking for the data-set, I would offend the author in some way and then he may not reply my email.

Let me know if you have any suggestion.

All the best,

-Linfeng