I read the Pro ASP.NET Core MVC 2 Seventh Edition book by Adam Freeman. In the code examples author uses the p-a-1 CSS-class of Bootstrap for the form tag, but I don't see such class for Bootstrap v3.3.7.
I assume that this is an obsolete class, but I can't find any information about it in Google. I also do not understand what name I am to use now instead of p-a-1 in Bootstrap v3.3.7.