diff --git a/README.md b/README.md
index 8a54ab2..4e3d2b7 100644
--- a/README.md
+++ b/README.md
@@ -23,8 +23,8 @@ You'll need Arduino desftop app 1.8.9 or later.
 | MQ-6 | Sparkfun | [datasheet](https://www.sparkfun.com/datasheets/Sensors/Biometric/MQ-6.pdf) |
 | MQ-7 | Sparkfun | [datasheet](https://www.sparkfun.com/datasheets/Sensors/Biometric/MQ-7.pdf) |
 | MQ-8 | Sparkfun | [datasheet](https://dlnmh9ip6v2uc.cloudfront.net/datasheets/Sensors/Biometric/MQ-8.pdf) |
-| MQ-9 | haoyuelectronics | [datasheet](http://www.haoyuelectronics.com/Attachment/MQ-9/MQ9.pdf) |
-| MQ-131 | sensorsportal | [datasheet](http://www.sensorsportal.com/DOWNLOADS/MQ131.pdf) |
+| MQ-9 | Haoyuelectronics | [datasheet](http://www.haoyuelectronics.com/Attachment/MQ-9/MQ9.pdf) |
+| MQ-131 | Sensorsportal | [datasheet](http://www.sensorsportal.com/DOWNLOADS/MQ131.pdf) |
 | MQ-135 | HANWEI Electronics | [datasheet](https://www.electronicoscaldas.com/datasheet/MQ-135_Hanwei.pdf) |
 | MQ-303A | HANWEI Electronics | [datasheet](http://www.kosmodrom.com.ua/pdf/MQ303A.pdf) |
 | MQ-309A | HANWEI Electronics | [datasheet](http://www.sensorica.ru/pdf/MQ-309A.pdf) |