Tampubolon et al. 1991, p. 344 Tampubolon, Sahala; Silalahi, P.H.; Nainggolan, Rustam Effendy; Siregar, Yamin; Simanjuntak, Hercules (1991). Tapanuli Utara Membangun. Tarutung: Government of North Tapanuli with the Karya Pembangunan Institute.
Tampubolon et al. 1991, pp. 344–345 Tampubolon, Sahala; Silalahi, P.H.; Nainggolan, Rustam Effendy; Siregar, Yamin; Simanjuntak, Hercules (1991). Tapanuli Utara Membangun. Tarutung: Government of North Tapanuli with the Karya Pembangunan Institute.
Tampubolon et al. 1991, p. 345 Tampubolon, Sahala; Silalahi, P.H.; Nainggolan, Rustam Effendy; Siregar, Yamin; Simanjuntak, Hercules (1991). Tapanuli Utara Membangun. Tarutung: Government of North Tapanuli with the Karya Pembangunan Institute.
Tampubolon et al. 1991, pp. 346–347 Tampubolon, Sahala; Silalahi, P.H.; Nainggolan, Rustam Effendy; Siregar, Yamin; Simanjuntak, Hercules (1991). Tapanuli Utara Membangun. Tarutung: Government of North Tapanuli with the Karya Pembangunan Institute.
Tampubolon et al. 1991, p. 340 Tampubolon, Sahala; Silalahi, P.H.; Nainggolan, Rustam Effendy; Siregar, Yamin; Simanjuntak, Hercules (1991). Tapanuli Utara Membangun. Tarutung: Government of North Tapanuli with the Karya Pembangunan Institute.
Tampubolon et al. 1991, p. 342 Tampubolon, Sahala; Silalahi, P.H.; Nainggolan, Rustam Effendy; Siregar, Yamin; Simanjuntak, Hercules (1991). Tapanuli Utara Membangun. Tarutung: Government of North Tapanuli with the Karya Pembangunan Institute.
Toba Pulp Lestari. "2018 Annual Report"(PDF). kpud-sumutprov.go.id (in Indonesian and English). Archived from the original(PDF) on 2020-06-25. Retrieved 2020-07-04.
web.archive.org
Toba Pulp Lestari. "2018 Annual Report"(PDF). kpud-sumutprov.go.id (in Indonesian and English). Archived from the original(PDF) on 2020-06-25. Retrieved 2020-07-04.