Documents required for sale of agriculture land

Hi, 

I am resident of belgaum, karnataka. The agriculture land is located in hattarki, Hukkeri taluq, Belgaum district, Karnataka, India. It was owned and in the name of my father ,who expired 20 years ago, he has a survivimg wife(i.e my mother) , 5 sons (i.e my brothers) . 

I would like to know which all documents would be required for the sale of the agriculture land and what is the detail procedure ?

I would really appreciate for the help in this regard.