There are lot of softwares to install which I have to type something like: -

sudo add-apt-repository ppa:smathot/cogscinl

Actually this is what I have to write when I am installing Zotero on Ubuntu 14.04.

The problem is that once I hit the Enter key, no progress takes place and the terminal does not show any activity for a long time and then it shows an error such as

upendra@upendra-Aspire-4738Z:~$ sudo add-apt-repository ppa:smathot/cogscinl
Cannot add PPA: 'ppa:smathot/cogscinl'.
Please check that the PPA name or format is correct.

The same kind of error pops up every time I try to install a software where this 'ppa' comes. Is there something wrong with the configuration?

Currently I access Internet via a proxy server of our college.

According to https://launchpad.net/~smathot/+archive/ubuntu/cogscinl
... you can also add the repo manually to /etc/apt/source.list
I.e. they are showing the right text to add :
>>> Technical details about this PPA
>>>
deb http://ppa.launchpad.net/smathot/cogscinl/ubuntu trusty main
deb-src http://ppa.launchpad.net/smathot/cogscinl/ubuntu trusty main