This is the 4990th most frequent Polish word.
polskimi
"Polskimi" means "Polish" in the instrumental plural form.
Here, 'polskimi' is an adjective in instrumental plural form, modifying the plural noun 'pisarzami' (authors). It implies that the authors are Polish.
Uwielbiam czytać książki napisane polskimi pisarzami.
I love reading books written by Polish authors.
In this sentence, 'polskimi' as an adjective in the instrumental plural form modifies 'drogami' (roads), showing that the roads were Polish.
Podróżowałem polskimi drogami podczas wakacji.
I traveled Polish roads during my vacation.
Here, 'polskimi' describes 'przyjaciółmi' (friends) in the instrumental plural case, denoting that the friends are Polish.