I've seen an occasional mention here of agreements between USA and some Schengen countries that can be used (if one is careful of details) for staying in a specific Schengen country after ninety days in others have run out. One of those countries (for US citizens) was Poland.
EU has published a list of such agreements but Poland is not mentioned. I'd like a URI for reliable descriptions of the details of these agreements, including Poland, if it exists. Perhaps a community answer allowing others to look for the agreements, or separate answers for each agreement.
See also US Citizen: 90/180 Schengen Stay & Bilateral Agreements w/Poland, Denmark, etc
EDIT: This might be a duplicate of Which Schengen countries have bilateral agreements which ignore the standard 90/180 rule?