diff --git a/src/Output/QRFpdf.php b/src/Output/QRFpdf.php
index 22c8f25a0..f4768e164 100644
--- a/src/Output/QRFpdf.php
+++ b/src/Output/QRFpdf.php
@@ -7,6 +7,12 @@ namespace chillerlan\QRCode\Output;
 use chillerlan\QRCode\Data\QRMatrix;
 use chillerlan\Settings\SettingsContainerInterface;
 
+/**
+ * QRFpdf output module (requires fpdf)
+ *
+ * @see https://github.com/Setasign/FPDF
+ * @see http://www.fpdf.org/
+ */
 class QRFpdf extends QROutputAbstract
 {
     public function __construct(SettingsContainerInterface $options, QRMatrix $matrix)