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docs/User-Manual.md

@@ -17,9 +17,11 @@ title: User Manual
 - [Language Details](#language-details)
 - [Multithreaded Programming](#multithreaded-programming)
 - [Foreign Function Interface](#foreign-function-interface)
+  - [Writing a Scheme Function in C](#writing-a-scheme-function-in-c)
   - [Writing a Scheme Function in C](#writing-a-scheme-function-in-c)
   - [Including a C Header File](#including-a-c-header-file)
   - [Linking to a C Library](#linking-to-a-c-library)
+  - [Calling Scheme Functions from C](#calling-scheme-functions-from-c)
 - [Licensing](#licensing)
 - [References and Further Reading](#references-and-further-reading)
 
@@ -216,6 +218,10 @@ Functions that may block must call the `set_thread_blocked` macro to let the sys
 
 The Cyclone runtime can be used as a reference for how to write your own C functions. A good starting point would be [`runtime.c`](../runtime.c) and [`types.h`](../include/cyclone/types.h).
 
+## Foreign Library
+
+The [`(cyclone foreign)`](api/cyclone/foreign) provides a convenient interface for integrating with C code, and provides higher-level constructs than `define-c`. See the API documentation for more information.
+
 ## Including a C Header File
 
 A C header may be included using the `include-c-header` special form. This special form may be used either as part of a library definition:
@@ -244,6 +250,12 @@ A Cyclone library may use the `c-linker-options` expression to instruct the comp
       (export curl-version)
       (c-linker-options "-lcurl")
 
+## Calling Scheme Functions from C
+
+C functions `Cyc_scm_call` and `Cyc_scm_call_no_gc` are provided to allow calling Scheme functions from C. 
+
+The best way to get started with these functions is with the code examples in the Cyclone source tree under [`examples/call-scm-from-c`](../examples/call-scm-from-c).
+
 # Licensing
 Cyclone is available under the [MIT license](http://www.opensource.org/licenses/mit-license.php).