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|---|---|---|
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| 0000919574-19-005953-index.html | 2019-09-20 09:13:38 | |
| 0000919574-19-005953.txt | 2019-09-20 09:13:38 | |
 0000919574-19-005953-xbrl.zip | 98767 | 2019-09-20 09:13:38 |
| d8374442_6-k.htm | 555254 | 2019-09-20 09:13:38 |
| FilingSummary.xml | 21399 | 2019-09-20 09:13:38 |
| Financial_Report.xlsx | 41909 | 2019-09-20 09:13:38 |
| nat-20190630.xml | 365554 | 2019-09-20 09:13:38 |
| nat-20190630.xsd | 31589 | 2019-09-20 09:13:38 |
| nat-20190630_cal.xml | 58182 | 2019-09-20 09:13:38 |
| nat-20190630_def.xml | 102887 | 2019-09-20 09:13:38 |
| nat-20190630_lab.xml | 423507 | 2019-09-20 09:13:38 |
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| R9.htm | 8511 | 2019-09-20 09:13:38 |
| report.css | 2766 | 2019-09-20 09:13:38 |
| Show.js | 1084 | 2019-09-20 09:13:38 |