You can lookup the names of the authors in a patents search engine such as Google Patents or PATENTSCOPE. Each patent application has three dates: filing date, publication date, and the issuing date. Once a patent has been filed, it becomes in a state called patent pending. In the US, a patent application is published after 18 months of the filing date and so people can loop it up using search engines. However, in the US, before that, there is no way to tell if the authors submitted a patent application other than asking them. However, that does not constitute a legal issue for you because the authors' work, in the US, is not protected until the patent is issued. So if you cannot find a patent using one of the search engines, it means that the work is not protected and it would still take several/many months for a patent to be issued. Note that in other countries, published patent applications may be protected even if a patent has not yet been granted.