| 출처 | http://jjalbox.com/vfstd |
| 출처 보완 |
Why isn't the world covered in poop? - Eleanor Slade and Paul Manning (2018.3.26)
https://youtu.be/uSTNyHkde08 - TED-Ed https://ed.ted.com/lessons/why-isn-t-the-world-covered-in-poop-eleanor-slade-and-paul-manning |
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