diff --git a/readme.md b/readme.md
index 00dc657..ecdaeae 100644
--- a/readme.md
+++ b/readme.md
@@ -98,18 +98,18 @@ Software tools for analyzing embedded/IoT devices and firmware.
 ## ZigBee Tools
 
 - [ApiMote](http://apimote.com) - ZigBee security research hardware for learning about and evaluating the security of IEEE 802.15.4/ZigBee systems. Killerbee compatible.
-- [Atmel RZUSBstick] - Discontinued product. Lucky if you have one! - Tool for development, debugging and demonstration of a wide range of low power wireless applications including IEEE 802.15.4, 6LoWPAN, and ZigBee networks. Killerbee compatible.
+- Atmel RZUSBstick - Discontinued product. Lucky if you have one! - Tool for development, debugging and demonstration of a wide range of low power wireless applications including IEEE 802.15.4, 6LoWPAN, and ZigBee networks. Killerbee compatible.
 - [Freakduino](https://freaklabsstore.com/index.php?main_page=product_info&cPath=22&products_id=219&zenid=fpmu2kuuk4abjf6aurt3bjnfk4) - Low Cost Battery Operated Wireless Arduino Board that can be turned into a IEEE 802.15.4 protocol sniffer.
 
 ## SDR Tools
-- [HackRF One](https://greatscottgadgets.com/harkrf/) - Software Defined Radio peripheral capable of transmission or reception of radio signals from 1 MHz to 6 GHz (half-duplex).
+- [HackRF One](https://greatscottgadgets.com/hackrf/) - Software Defined Radio peripheral capable of transmission or reception of radio signals from 1 MHz to 6 GHz (half-duplex).
 - [YardStick One](https://greatscottgadgets.com/yardstickone/) - Half-duplex sub-1 GHz wireless transceiver.
 - [LimeSDR](https://www.crowdsupply.com/lime-micro/limesdr) - Software Defined Radio peripheral capable of transmission or reception of radio signals from 100 KHz to 3.8 GHz (full-duplex).
 - [BladeRF 2.0](https://www.nuand.com/bladerf-2-0-micro/) - Software Defined Radio peripheral capable of transmission or reception of radio signals from 47 MHz to 6 GHz (full-duplex).
 - [USRP B Series](https://www.ettus.com/product-categories/usrp-bus-series/) - Software Defined Radio peripheral capable of transmission or reception of radio signals from 70 MHz to 6 GHz (full-duplex).
 
-##RFID NFC Tools
-- [Proxmark 3 RDV4](https://www.proxmark.com/) - Powerful general purpose RFID tool. From Low Frequency (125kHz) to High Frequency (13.56MHz) tags
+## RFID NFC Tools
+- [Proxmark 3 RDV4](https://www.proxmark.com/) - Powerful general purpose RFID tool. From Low Frequency (125kHz) to High Frequency (13.56MHz) tags.
 - [ChamaleonMini](http://chameleontiny.com/) - Programmable, portable tool for NFC security analysis.
 - [HydraNFC](https://hydrabus.com/hydranfc-1-0-specifications/) - Powerful 13.56MHz RFID / NFC platform. Read / write / crack / sniff / emulate.
 
@@ -121,13 +121,13 @@ Software tools for analyzing embedded/IoT devices and firmware.
 - 2019, Aditya Gupta: [The IoT Hacker's Handbook: A Practical Guide to Hacking the Internet of Things](https://www.apress.com/us/book/9781484242995)
 - 2018, Mark Swarup Tehranipoor: [Hardware Security: A Hands-on Learning Approach](https://www.elsevier.com/books/hardware-security/bhunia/978-0-12-812477-2)
 - 2018, Mark Carney: [Pentesting Hardware - A Practical Handbook (DRAFT)](https://github.com/unprovable/PentestHardware)
-- 2018,  Qing Yang, Lin Huang [Inside Radio: An Attack and Defense Guide](https://www.amazon.com/Inside-Radio-Attack-Defense-Guide-ebook/dp/B07BKVKL87/)
+- 2018,  Qing Yang, Lin Huang [Inside Radio: An Attack and Defense Guide](https://link.springer.com/book/10.1007/978-981-10-8447-8)
 - 2017, Aditya Gupta, Aaron Guzman: [IoT Penetration Testing Cookbook](https://www.packtpub.com/networking-and-servers/iot-penetration-testing-cookbook)
 - 2017, Andrew Huang: [The Hardware Hacker: Adventures in Making and Breaking Hardware](https://nostarch.com/hardwarehackerpaperback)
 - 2016, Craig Smith: [The Car Hacker's Handbook: A Guide for the Penetration Tester](https://nostarch.com/carhacking)
-- 2015, Keng Tiong Ng: [The Art of PCB Reverse Engineering](https://www.amazon.com/Art-PCB-Reverse-Engineering-Standard/dp/151880053X/)
+- 2015, Keng Tiong Ng: [The Art of PCB Reverse Engineering](https://visio-for-engineers.blogspot.com/p/order.html)
 - 2015, Nitesh Dhanjan: [Abusing the Internet of Things: Blackouts, Freakouts, and Stakeouts](https://shop.oreilly.com/product/0636920033547.do)
-- 2015, Joshua Wright , Johnny Cache: [Hacking Wireless Exposed](https://www.amazon.com/Joshua-Wright-ebook/dp/B00U1Y17OI/) 
+- 2015, Joshua Wright , Johnny Cache: [Hacking Wireless Exposed](https://www.mhprofessional.com/9780071827638-usa-hacking-exposed-wireless-third-edition-group) 
 - 2014, Debdeep Mukhopadhyay: [Hardware Security: Design, Threats, and Safeguards](https://www.taylorfrancis.com/books/9780429066900)
 - 2014, Jack Ganssle: [The Firmware Handbook (Embedded Technology)](https://www.elsevier.com/books/the-firmware-handbook/ganssle/978-0-7506-7606-9)
 - 2013, Andrew Huang: [Hacking the XBOX](https://nostarch.com/xboxfree)