Wahyuni, Sri, 		Supriyanto, Supriyanto, AND 		Djayus, Djayus.
" ESTIMASI SEBARAN KUALITAS BATUBARA (ASH CONTENT) MENGGUNAKAN METODE INVERS DISTANCE WEIGHTED (IDW) DAN ORDINARY KRIGING (OK) DI PT. KAYAN PUTRA UTAMA COAL SITE SEPARI, KALIMANTAN TIMUR" <em>GEOSAINS KUTAI BASIN</em> [Online], Volume 2 Number 1 (12 April 2019)