Minor fixes

src/references.bib

@@ -19,7 +19,7 @@
 }
 
 @ONLINE{HTU21D, 
-	title={HPC199-3 HTU21D(F) Sensor Datasheet},
+	title={{HPC199-3 HTU21D(F)} Sensor Datasheet},
 	author={Measurement Specialties, Inc},
 	url={https://cdn-shop.adafruit.com/datasheets/1899_HTU21D.pdf},
 	urldate={2020-04-03},
@@ -27,7 +27,7 @@
 }
 
 @ONLINE{SI7021, 
-	title={Si7021-A20 Sensor Datasheet Rev. 1.2},
+	title={{Si7021-A20} Sensor Datasheet Rev. 1.2},
 	author={{Silicon Laboratories Inc.}},
 	url={https://www.silabs.com/documents/public/data-sheets/Si7021-A20.pdf},
 	urldate={2020-04-03},
@@ -35,7 +35,7 @@
 }
 
 @ONLINE{HDC2080, 
-	title={HDC2080 Sensor Datasheet},
+	title={{HDC2080} Sensor Datasheet},
 	author={{Texas Instruments}},
 	url={https://www.ti.com/lit/ds/symlink/hdc2080.pdf},
 	urldate={2020-04-03},
@@ -43,7 +43,7 @@
 }
 
 @ONLINE{BME280, 
-	title={BME280 Sensor Datasheet},
+	title={{BME280} Sensor Datasheet},
 	author={{Bosch Sensortec}},
 	url={https://www.bosch-sensortec.com/media/boschsensortec/downloads/datasheets/bst-bme280-ds002.pdf},
 	urldate={2020-04-03},
@@ -51,13 +51,13 @@
 }
 
 @ONLINE{MQ135, 
-	title={MQ-135 GAS SENSOR Technical Data},
+	title={{MQ-135} GAS SENSOR Technical Data},
 	url={https://www.olimex.com/Products/Components/Sensors/Gas/SNS-MQ135/resources/SNS-MQ135.pdf},
 	urldate={2020-04-03},
 }
 
 @ONLINE{CCS811, 
-	title={CCS811 Datasheet},
+	title={{CCS811} Datasheet},
 	author={{ams AG}},
 	url={https://cdn-shop.adafruit.com/product-files/3566/3566_datasheet.pdf},
 	urldate={2020-04-03},
@@ -65,7 +65,7 @@
 }
 
 @ONLINE{SGP30, 
-	title={SGP30 Datasheet},
+	title={{SGP30} Datasheet},
 	author={{Sensirion AG}},
 	url={https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/9_Gas_Sensors/Datasheets/Sensirion_Gas_Sensors_SGP30_Datasheet.pdf},
 	urldate={2020-04-03},