1\begin{thebibliography}{1}
2\bibitem{gmi}
4{Global Market Insights}.
5\newblock High density polyethylene (hdpe) market size.
6\newblock
7 \url{https://www.gminsights.com/industry-analysis/high-density-polyethylene-HDPE-market},
8 2017.
9\newblock [Online; accessed 20-May-2018].
10\bibitem{fig1}
12Thorsten Graunke, Katrin Schmitt, and J~Wöllenstein.
13\newblock Organic membranes for selectivity enhancement of metal oxide gas
14 sensors.
15\newblock 2016:1--22, 01 2016.
16\bibitem{pubchem}
18{National Center for Biotechnology Information}.
19\newblock Pubchem compound database; cid=6325.
20\newblock \url{https://pubchem.ncbi.nlm.nih.gov/compound/6325}.
21\newblock [Online; accessed 20-May-2018].
22\bibitem{nzmfg}
24{New Zealand Institute of Chemistry}.
25\newblock The manufacture of polyethylene.
26\newblock
27 \url{https://web.archive.org/web/20180223141558/http://www.nzic.org.nz/ChemProcesses/polymers/10J.pdf}.
28\newblock [Online; accessed 23-May-2018].
29\bibitem{macrog}
31{Polymer Science Learning Centre}.
32\newblock Polyethylene.
33\newblock \url{http://www.pslc.ws/macrog/pe.htm}.
34\newblock [Online; accessed 23-May-2018].
35\bibitem{wiki:xxx}
37{Wikipedia contributors}.
38\newblock High-density polyethylene --- {Wikipedia}{,} the free encyclopedia.
39\newblock \url{https://en.wikipedia.org/wiki/High-density_polyethylene}, 2018.
40\newblock [Online; accessed 20-May-2018].
41\end{thebibliography}