Funding for this research was provided by:
Ministry of the Environment (FY2003-2007, S2-2b)
Received: 28 August 2018
Accepted: 8 May 2019
First Online: 3 June 2019
: Dr. Herwint Simbolon, who was a core member of our research team, suddenly passed away in 2011. We offer him our sincerest condolences and this paper.
: The authors declare that they have no competing interests.
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