Subchapter display in the TOC (Table of contents) of the springer lncs template [closed]

Question

I'm editing a proceeding frontmatter under the springer lncs template. Using the command of \addtocmark{xx}, i can add the top level chapter name in the "Table of contents". Now, I want to add the second level chapter names in the TOC. How can i achieve it.

For example:

Table of Content

Chapter 1

chapter 1.1

xxx11 ..................................16

[author names]

xxx12 ..................................24

[author names] .... .... ....

thanks!