I created the tags (surface-integrals) and (line-integrals).
I had created the (line-integrals) before and had wrote its wiki only to have the tag deleted by someone and consequently the wiki itself.
I feel like these tags are useful (and necessary too, but necessity isn't a necessary reason to create a tag). I don't feel like explaining why I find these tags useful. I'm just letting the community know the tags were created, now do as you see fit.