FIG. 1 is a front, top perspective view of sides of a mattress according to a first embodiment of the present design;
FIG. 2 is a left side view of the sides of a mattress of FIG. 1, with an enlarged fragmentary view of a portion of the design, the right side view being a mirror image of the left side view;
FIG. 3 is a rear view of the sides of a mattress of FIG. 1, the front view being a mirror image thereof;
FIG. 4 is a front, top perspective view of sides of a mattress according to a second embodiment of the present design;
FIG. 5 is a left side view of the sides of a mattress of FIG. 4, with an enlarged fragmentary view of a portion of the design, the right side view being a mirror image of the left side view;
FIG. 6 is a rear view of the sides of a mattress of FIG. 4, the front view being a mirror image thereof;
FIG. 7 is an enlarged fragmentary view taken from the right side edge in FIG. 2; and,
FIG. 8 is an enlarged fragmentary view taken from the right side edge in FIG. 5.
The broken lines depict environment subject matter only and form no part of the claimed design.