These are the sixteen selection patterns from here implemented in terms of S7:
nand-equivalents
In terms of familiar functions, S7 is NAND. So all sixteen selections written as NAND functions would be:

S0 (NAND (NAND $1 (NAND $1 $1)) (NAND $1 (NAND $1 $1)))
S1 (NAND (NAND (NAND $1 $1) (NAND $2 $2)) (NAND $1 (NAND $1 $1)))
S2 (NAND (NAND (NAND $1 $1) $2) (NAND $1 (NAND $1 $1)))
S3 (NAND $1 $1)
S4 (NAND (NAND $1 (NAND $1 $2)) (NAND $1 (NAND $1 $1)))
S5 (NAND $2 $2)
S6 (NAND (NAND (NAND $1 $1) $2) (NAND $1 (NAND $1 $2)))
S7 (NAND $1 $2)
S8 (NAND (NAND $1 $2) (NAND $1 $2))
S9 (NAND (NAND $1 $2) (NAND (NAND $1 $1) (NAND $2 $2)))
S10 (NAND (NAND $1 $2) (NAND $2 $2))
S11 (NAND $1 (NAND $1 $2))
S12 (NAND (NAND $1 $1) (NAND $1 $1))
S13 (NAND (NAND $1 $1) $2)
S14 (NAND (NAND $1 $1) (NAND $2 $2))
S15 (NAND $1 (NAND $1 $1))))

Note that S10 can also be written more simply as $1 and S12 as $2.