Maybe someone here can help me to solve a mystery. I have some conflicting information and being pretty inexperienced in genealogy, I'm not sure how to determine which is true. Everyone seems to agree that my great grandfather's name was Frederik Nielsen JENSEN but I've got a couple different variations on my great grandmother's name.

Anna Frederika Petersen
or
Anna Helena Vilhelmina Petersson

Research through LDS has records for both of the above married Frederik Nielsen JENSEN on June 15, 1867. There's even a family listed for Frederik and Anna Helena Vilhelmina Petersson but my grandmother, Selma Emilia JENSEN (born Jan 3, 1880 in Logan, UT) is not listed as one of their children. Any suggestions from fellow researchers of this area with more experience than my one month? Thanks for any and all help.