Lindy, adding a heading (of any level, by the way) will not necessarily result in automatic display of table of contents. The way it works is that if there are 4 headings then the table of contents will display automatically.
There are ways to either force or suppress display of table of contents, regardless of the number of headings there are, which is a better way to accomplish what you are doing by adding a superfluous heading. Without your extraneous heading, if the table of contents is displayed then the Sources heading will be the link you want to jump directly there.
To manually override the defaults, put the following on the top line of the text area:
__TOC__ (that's 2 underscores, upper case TOC, and 2 more underscores) to always show it
__NOTOC__ (that's 2 underscores, uppercase NOTOC, and 2 more underscores) to never show it