[ 출처 : 출처 : http://www.iring.ca/_Knowledgebase/module_4_5_2_print.html ,
https://www.sciencedirect.com/science/article/abs/pii/S2095268615000609 ,
https://www.researchgate.net/figure/Wolverine-underground-11-drilling-pattern-Length-is-in-meter-YZC-2013_fig13_271274704 ]