51![](https://www.pdfsearch.io/img/d307cb66905c5adf24da1ca4f9c6882f.jpg) | Add to Reading ListSource URL: www.niac.usra.eduLanguage: English - Date: 2012-10-10 14:59:03
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52![](https://www.pdfsearch.io/img/216518d6b6d57e9c13f12394428c9ac0.jpg) | Add to Reading ListSource URL: www.askmar.comLanguage: English - Date: 2009-01-01 23:42:02
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53![](https://www.pdfsearch.io/img/a04148415600257c89d715d3977fb261.jpg) | Add to Reading ListSource URL: www.icarusinterstellar.orgLanguage: English - Date: 2011-02-09 19:11:01
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54![](https://www.pdfsearch.io/img/b67a7278453d61df2bf758942ca01c53.jpg) | Add to Reading ListSource URL: arxiv.orgLanguage: English - Date: 2011-09-26 20:02:19
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55![](https://www.pdfsearch.io/img/85cc3dd97b9a67b92ddf1d70d0aba9a6.jpg) | Add to Reading ListSource URL: www.engr.psu.eduLanguage: English - Date: 2001-02-28 17:43:27
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56![](https://www.pdfsearch.io/img/e982e293c4f1f2fe769f90acf34e35cc.jpg) | Add to Reading ListSource URL: arxiv.orgLanguage: English - Date: 2011-09-26 20:02:19
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