Revert "remove "induction constant" and "dependent type""

This reverts commit 77fa9e7f1cc1df2111a4eb4b64e48bc1f71553bb.
Revert "more references"

This reverts commit 5a50ecc7aaed690df14d115e9c2dd25cfb769897.
@martinescardo somehow managed to accidentally add a bunch of `.svn` directories,
and he resurrected the `obsolete` directory. I think this is a combination of two
things:

1. He used the wrong directory on his computer, one that contained the book in a svn repository.

2. He followed the `GIT_CHEATSHEET.TXT` which says people should use `git add --all`. I was always
   woried about this, and it seems rightfully so. I am going to change the instructions.

Conflicts:
	.svn/all-wcprops
	.svn/entries
	.svn/text-base/back.aux.svn-base
	.svn/text-base/main.blg.svn-base
	.svn/text-base/main.brf.svn-base
	.svn/text-base/main.fdb_latexmk.svn-base
	.svn/text-base/main.log.svn-base
	.svn/text-base/main.pdf.svn-base
	.svn/text-base/main.toc.svn-base
	.svn/text-base/preliminaries.aux.svn-base
	.svn/text-base/preliminaries.tex.svn-base
	preliminaries.tex
	references.bib