EDIT

This question is not at all a duplicate of How to downgrade from LibreOffice 4.0 to 3.6?

1. The above mentioned question talks about downgrading from a specific version of LibreOffice, namely from 4.0 to 3.6. The solutions mentioned are not the ones I am looking for. They will work but I wanted a general solution without using PPA or downloading .deb files for from a higher version to a lower version.
2. The above solutions suggest either downloading .deb files for LibreOffice 3.6 or adding repository for it. Furthermore, some of the answers put out-of-proportion~(applicable for the solution, however) stress on use of synaptic, not general command-line-solution.
3. That made me wonder, at this very moment, if I take a fresh computer, and install Ubuntu 12.04, LibreOffice installation will work without a hitch. Then why I can not install LibreOffice in my 12.04 machine today from simple command line?
4. This answer to my question, clarified everything. I need to use ppa-purge so that this resets all packages from a PPA to the standard versions released for my distribution. Basically it is like a way to restore my system back to the way it was before my installed packages from a PPA. This article further elaborates the idea.
5. The above mentioned answer worked perfectly for me. Actually, this was an education for me since it taught me how do downgrade a package that was added via PPA.

I had upgraded from LibreOffice 3 to LibreOffice 4 using the PPA.

Now since I found that LibreOffice 4 has some issues, including handling my native language, I want to move back to LibreOffice 3.

In order to accomplish this, I removed the LibreOffice config directory from my home and then purged LibreOffice from my machine.

sudo apt-get purge libreoffice-*

Then I removed the relevant PPA's using the sudo apt-add-repository --remove command. And then ran sudo apt-get update.

Now, when I try to install LibreOffice using the command

sudo apt-get install libreoffice

I get an avalanche of output about unmet dependencies, something like,

The following packages have unmet dependencies:
 libreoffice : Depends: libreoffice-core (= 1:3.5.7-0ubuntu4) but it is not going to be installed
(snipped)

If I dig the issue further, by using the command,

sudo apt-get install libreoffice-core

I get

The following packages have unmet dependencies:  libreoffice-core :
Depends: libreoffice-common (> 1:3.5.7) but it is not going to be
installed
                Depends: libexttextcat0 (>= 2.2-8) but it is not going to be installed
                Depends: ure (>= 3.5.7~) but it is not going to be installed E: Unable to correct problems, you have held broken packages.

Could you please tell me how do I install LibreOffice 3 in my machine?

I am using Ubuntu 12.04 LTS.