In 1746, Pavel Doležal published a grammar book of the common language of Czechs and Slovaks

When working on his specialist publication, the handbook of the common standard language of Czechs and Slovaks – Grammatica Slavico-Bohemica, Pavel Doležal (1700 – 1778), a teacher and grammarian, based his work on the Slovak language spoken in the Skalica region (currently considered to be a dialect). Just like a contemporary linguist Ľubomír Ďurovič points out, the Skalica dialect was considered to be the most cultivated forms of the Slovak language in the 18th century.

You can read more about this topic in this blog post written by Roman Kebísek.