Analisis ketentuan kesalahan berat dalam perjanjian kerja bersama PT. X (studi kasus putusan Mahkamah Agung Republik Indonesia nomor 110/PK/PDT.SUS/2010) = Analysis of the serious mistakes provisions in collective labour agreements PT. X (a study of the supreme court of the Republic of Indonesia decision no 110/PK/PDT.SUS/2010)