diff --git a/ledger/file.go b/ledger/file.go
index dd6e72f..fc34331 100644
--- a/ledger/file.go
+++ b/ledger/file.go
@@ -257,6 +257,7 @@ func isNumericByte(b byte) bool {
 	return '0' <= b && b <= '9' || b == '.' || b == '-'
 }
 
+// from "[^\n]*\n?.*" read "[^\n]*\n?"
 func readTransactionValueCurrency(r io.Reader) (io.Reader, float64, string, error) {
 	return nil, 0, "", errors.New("not impl read a value currency")
 }