Penunjukan langsung anak perusahaan dalam pengadaan barang dan/atau jasa di lingkungan PT Pertamina (Persero) ditinjau dari hukum persaingan usaha = Analysis of direct appointment of the subsidiary company of Pertamina (Persero) in procurement of goods and or services based on competition law / Margaretha Isabela Siregar - Siregar, Margaretha Isabela, author (Fakultas Hukum Universitas Indonesia, 2013)