diff --git a/cmd/primitiveRoot.go b/cmd/primitiveRoot.go
index 3bf640e..329415a 100644
--- a/cmd/primitiveRoot.go
+++ b/cmd/primitiveRoot.go
@@ -144,7 +144,9 @@ var primitiveRootCmd = &cobra.Command{
 
 This command computes a value g such that, for all integers a coprime to n, g^k = a (mod n) for some k. In other words, this command computes a generator for the multiplicative group of integers modulo n.
 
-For improved performance, provide the prime factorization of the totient of n with the -t flag.`,
+For improved performance, provide the prime factorization of the totient of n with the -t flag.
+
+Note that primitive roots only exist for the moduli 1, 2, 4, p^k, and 2p^k, where p is an odd prime. The totients of these numbers are 1, 1, 2, (p-1)*p^(k-1), and (p-1)*p^(k-1), respectively.`,
 	Run: primitiveRoot,
 }
 
@@ -165,4 +167,5 @@ func init() {
 	primitiveRootCmd.MarkFlagRequired("modulus")
 
 	primitiveRootCmd.Flags().StringSliceVarP(&tpf, "totient-factorization", "t", make([]string, 0), "prime factorization of the totient of the modulus")
+	// TODO: add a check flag for verifying -t input is the totient, test for performance
 }