Please read the following table in HTML format from a webpage and then answer the question in detail according to the table. Each table cell is defined by a <td> and a </td> tag. Each table row starts with a <tr> and ends with a </tr> tag. 'rowspan=m' and 'colspan=n' represents a cell spaning over 'm' rows and 'n' columns.

Webpage title:
The Legend of Korra
Table title:
Series overview
Table:
<table id='hittask' contenteditable='False'>
<tr> <th colspan=2 rowspan=2 > Season </th><th colspan=1 rowspan=2 > Book </th><th colspan=2 rowspan=2 > Episodes </th><th colspan=3 rowspan=1 > Originally aired </th></tr>
<tr> <th colspan=1 rowspan=1 > First aired </th><th colspan=1 rowspan=1 > Last aired </th><th colspan=1 rowspan=1 > Network </th></tr>
<tr> <td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 > 1 </td><td colspan=1 rowspan=1 > Book One: Air </td><td colspan=2 rowspan=1 > 12 </td><td colspan=1 rowspan=1 > April 14, 2012 </td><td colspan=1 rowspan=1 > June 23, 2012 </td><td class="highlighted"  colspan=1 rowspan=2 > Nickelodeon </td></tr>
<tr> <td colspan=1 rowspan=1 >  </td><td class="highlighted"  colspan=1 rowspan=1 > 2 </td><td class="highlighted"  colspan=1 rowspan=1 > Book Two: Spirits </td><td colspan=2 rowspan=1 > 14 </td><td class="highlighted"  colspan=1 rowspan=1 > September 13, 2013 </td><td colspan=1 rowspan=1 > November 22, 2013 </td></tr>
<tr> <td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 > 3 </td><td colspan=1 rowspan=1 > Book Three: Change </td><td colspan=2 rowspan=1 > 13 </td><td colspan=1 rowspan=1 > June 27, 2014 </td><td colspan=1 rowspan=1 > August 22, 2014 </td><td colspan=1 rowspan=1 > Nickelodeon Nick.com </td></tr>
<tr> <td colspan=1 rowspan=1 >  </td><td colspan=1 rowspan=1 > 4 </td><td colspan=1 rowspan=1 > Book Four: Balance </td><td colspan=2 rowspan=1 > 13 </td><td colspan=1 rowspan=1 > October 3, 2014 </td><td colspan=1 rowspan=1 > December 19, 2014 </td><td colspan=1 rowspan=1 > Nick.com </td></tr>
</table>
Question:
When did the second season of Book Two: Spirits begin airing and on what network?
Answer:
The second season (Book Two: Spirits) began airing on Nickelodeon on September 13, 2013.