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:
List of mayors and city managers of Cambridge, Massachusetts
Table title:
City managers
Table:
<table id='hittask' contenteditable='False'>
<tr> <th colspan=1 rowspan=1 > # </th><th colspan=1 rowspan=1 > City Manager </th><th colspan=1 rowspan=1 > Term </th><th colspan=1 rowspan=1 > Notes </th></tr>
<tr> <td colspan=1 rowspan=1 > 1st </td><td colspan=1 rowspan=1 > John B. Atkinson </td><td colspan=1 rowspan=1 > 1942 – 1952 </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > 2nd </td><td colspan=1 rowspan=1 > John J. Curry </td><td colspan=1 rowspan=1 > 1952 – 1966 </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > 3rd </td><td colspan=1 rowspan=1 > Joseph DeGuglielmo </td><td colspan=1 rowspan=1 > 1966 – 1968 </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > 4th </td><td class="highlighted"  colspan=1 rowspan=1 > James Sullivan </td><td class="highlighted"  colspan=1 rowspan=1 > 1968 – 1970 </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > 5th </td><td colspan=1 rowspan=1 > John H. Corcoran </td><td colspan=1 rowspan=1 > 1970 – 1974 </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > 6th </td><td class="highlighted"  colspan=1 rowspan=1 > James Sullivan </td><td class="highlighted"  colspan=1 rowspan=1 > 1974 – 1981 </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > 7th </td><td colspan=1 rowspan=1 > Robert W. Healy </td><td colspan=1 rowspan=1 > 1981 – 2013 </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > 8th </td><td colspan=1 rowspan=1 > Richard Rossi </td><td colspan=1 rowspan=1 > 2013 – 2016 </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > 9th </td><td colspan=1 rowspan=1 > Louis D. DePasquale </td><td colspan=1 rowspan=1 > 2016 – present </td><td colspan=1 rowspan=1 >  </td></tr>
</table>
Question:
When did James Sullivan serve as City Manager?
Answer:
James Sullivan served as the City Manager of Cambridge, Massachusetts from 1968 to 1970 and again from 1974 to 1981.