Help Regarding Writing A Letter To HR After Selecting Interview

Dear All,
I have attended an interview on __ date and received an email from HR dept saying that i have been shortlisted for the position and can expect a call shortly...Its about 3 weeks now and i need help regarding how to write a follow up mail....to enquire about when will i be expected to join....or info regarding it....

Dear ,
The proposed text for followup mail from you may as -
Dear Sir,
With reference to your mail dtd............ regarding intimation of shortlisting of my candidature for the position............
This is to bring in your kind notice that i was informed to receive a call for further proceedings, but as on date i haven't received any communication.
Thus, here I would like to show my keen interest and anticipation towards communication from your end.
Waiting for you response.
Thanks