Perbedaan pengaturan peningkatan nilai tambah menurut Undang-Undang Nomor 4 tahun 2009 tentang pertambangan mineral dan batubara dan dampaknya terhadap investasi pertambangan tembaga di Indonesia : studi kasus kontrak karya PT. Freeport Indonesia company = The difference regulations of increasing added value according to the Law No. 4 of 2009 and its impact to the copper investment in Indonesia : case study contract of work of PT. Freeport Indonesia Company