In Guadiya-Kanthahara, the following text of Madhva's is quoted:
What is to be known as sastra or scripture?
2. 43
rg-yajum-samatharva-sca bharatam pa-caratrakam
mula-ramayana-scaiva saastramityabhidhiyate
yacchanukulametasya taccha saastram prakirtitam
ato'nya grasthavistaro naiva sastram kurvatmatat
"The Rig, Yajur, Sama, and Atharva Vedas, as well as the Mahabharata, the Narada-Pa-caratra, and the Mula-Ramayana , are certainly known as shastra, or revealed scripture. Those books that favorably follow in the footsteps of these authorized literatures are also designated as shastra. All other literatures (which are not in pursuance of these authorized scriptures) simply lead one down the wrong path, and can never be known as scriptures." (Madhva-Bhashyadhrita Skandavacana)