diff --git a/docs/csaf_provider.md b/docs/csaf_provider.md
index 464f0db..4db4d31 100644
--- a/docs/csaf_provider.md
+++ b/docs/csaf_provider.md
@@ -112,6 +112,16 @@ The following example file documents all available configuration options:
 #   If this test fails the expression fails. If the
 #   test succeeds the rules are applied recursively to
 #   collect all strings in the result.
+#   If the result of the expression is a string this string
+#   is used. If the result is an array each element of
+#   this array is tested if it is a string or an array.
+#   If this test fails the expression fails. If the
+#   test succeeds the rules are applied recursively to
+#   collect all strings in the result.
+#   Suggested expressions are:
+#   - vendor, product family and product names:  "expr:$.product_tree..branches[?(@.category=='vendor' || @.category=='product_family' || @.category=='product_name')].name"
+#   - CVEs: "expr:$.vulnerabilities[*].cve"
+#   - CWEs: "expr:$.vulnerabilities[*].cwe.id"
 # Strings not starting with `expr:` are taken verbatim.
 # By default no category documents are created.
 # This example provides an overview over the syntax,
diff --git a/util/json.go b/util/json.go
index d21b4cf..985c7e1 100644
--- a/util/json.go
+++ b/util/json.go
@@ -101,8 +101,8 @@ func StringMatcher(dst *string) func(any) error {
 	}
 }
 
-// StringTreeMatcher returns a matcher which addis strings from
-// strings and recursively from arrays of strings.
+// StringTreeMatcher returns a matcher which adds strings
+// to a slice and recursively strings from arrays of strings.
 func StringTreeMatcher(strings *[]string) func(any) error {
 	// Only add unique strings.
 	unique := func(s string) {
@@ -179,8 +179,8 @@ func (pe *PathEval) Match(matcher []PathEvalMatcher, doc any) error {
 }
 
 // StringsFromTree returns strings from the given exprs.
-//  1. If a expression results a string this string is used.
-//  2. if a expression results in an array the elements
+//  1. If an expression results in a string this string is used.
+//  2. if an expression results in an array the elements
 //     of this array are recursively treated with 1. and 2.
 func (pe *PathEval) StringsFromTree(
 	exprs []string,