WHAT ARE THE 18 UPA PURANAS?

The following are the 18 upa purANas:
(1) sanatkumAram
(2) nArasimham
(3) nAradIyam
(4) Sivam
(5) durvAsasam
(6) kApilam
(7) mAnavam
(8) AuSAnasam
(9) varuNam
(10) kAlikA
(11) Sambham
(12) nandikeSvaram
(13) sauram
(14) pArASaram
(15) Adityam
(16) mAheSvaram
(17) bhAgavatam
(18) vaSishtham