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| 0001564590-19-017599-index.html | 2019-05-09 08:25:01 | |
| 0001564590-19-017599.txt | 2019-05-09 08:25:01 | |
 0001564590-19-017599-xbrl.zip | 126933 | 2019-05-09 08:25:01 |
| atra-10q_20190331.htm | 2185534 | 2019-05-09 08:25:01 |
| atra-20190331.xml | 1669371 | 2019-05-09 08:25:01 |
| atra-20190331.xsd | 47646 | 2019-05-09 08:25:01 |
| atra-20190331_cal.xml | 71623 | 2019-05-09 08:25:01 |
| atra-20190331_def.xml | 151191 | 2019-05-09 08:25:01 |
| atra-20190331_lab.xml | 422273 | 2019-05-09 08:25:01 |
| atra-20190331_pre.xml | 304808 | 2019-05-09 08:25:01 |
| atra-ex311_11.htm | 16305 | 2019-05-09 08:25:01 |
| atra-ex312_10.htm | 16313 | 2019-05-09 08:25:01 |
| atra-ex321_7.htm | 7718 | 2019-05-09 08:25:01 |
| FilingSummary.xml | 29763 | 2019-05-09 08:25:01 |
| Financial_Report.xlsx | 56721 | 2019-05-09 08:25:01 |
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| report.css | 2767 | 2019-05-09 08:25:01 |
| Show.js | 1085 | 2019-05-09 08:25:01 |