Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Species | Strain | Type | Base Pairs | Genes | Reference |
| --- | --- | --- | --- | --- | --- |
| Fervidobacterium nodosum | Rt17-B1 | Thermotogae | 1,950,000 | 1750.0 | 2009 |
| Kosmotoga olearia | TBF 19.5.1 | Thermotogae | 2,302,126 | 2118.0 | 2011 |
| Mesotoga prima | MesG1.Ag.4.2 | Thermotogae | 2,974,229 chromosome 1,724 plasmid | 2736.0 | 2012 |
| Thermosipho africanus | TCF52B | Thermotogae | 2,016,657 | 2000.0 | 2009 |
| Thermosipho melanesiensis | BI429 | Thermotogae | 1,920,000 | 1879.0 | 2009 |
| Thermotoga lettingae | TMO | Thermotogae | 2,140,000 | 2040.0 | 2009 |
| Thermotoga maritima | MSB8 | Thermotogae | 1,860,725 | 1846.0 | 1999, 2013 |
| Thermotoga petrophila | RKU-1 | Thermotogae | 1,820,000 | 1785.0 | 2009 |
Question:
what is the reference when the strain is msb8?
Answer:
1999, 2013