Who can initiate an optional referendum at the national level?

Constitutional Law onReferendum (Enacted in 1995) 

http://www.legislationline.org/documents/id/6770

(Official English Translation)

Article 8. Right to appoint referendum

The right toappoint referendum in the Republic of Tajikistan belongs to the President ofthe Republic of Tajikistan and Majlisi Namoyandagon Majlisi Oli of the Republicof Tajikistan.

Article 9. Initiative on proposing referendum

[...] Initiative onproposing referendum, except the issues mentioned in part 1 of the presentArticle belongs to not less than 1/3 of total number of members of MajlisiMilli Majlisi Oli of the Republic of Tajikistan or not less than 1/3 of totalnumber of deputies of Majlisi Namoyandagon Majlisi Oli of the Republic ofTajikistan.

President may call for areferendum, but does not have a say in the initiation of a referendum when thesubject does not pertain to constitutional amendments.