Salesforce – FTP Integration (Data loader, Web service & HTTP) – Ye Meri Life Hai – Chirag Mehta
Inbound and Outbound Web Services in Salesforce - Forcetalks
Salesforce Integration Tutorial Part 12 - Creating a SOAP Web Service in Apex - SFDC Stop
Continuation in Salesforce - Asynchronous Callout option for long running requests - Technical Potpourri from Sudipta Deb
Salesforce Trailhead - Apex Web Services - YouTube
Custom Apex WebService using REST - World Of Salesforce
How to call an external REST API to get data from API and passing the variables from REST API to apex method in Salesforce using Apex REST Post Methods | How to
Saurabh's Salesforce Blog: Calling External Web Services from Salesforce.com – Part III: Building an Apex class that calls your web service
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Salesforce Developer Tutorial: Get Started With Salesforce Programming | Edureka
SOAP Web Services
Activating Webservices – Propertybase Salesforce
Salesforce – Wikipedia
Building a Web Service Wrapper for Delegated Authentication using AWS Lambda – Venkat's Playspace