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diff --git a/docs/reference/src/api/util/nng_msleep.md b/docs/reference/src/api/util/nng_msleep.md
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+# nng_msleep
+
+## NAME
+
+nng_msleep --- sleep milliseconds
+
+## SYNOPSIS
+
+```c
+#include <nng/nng.h>
+#include <nng/supplemental/util/platform.h>
+
+void nng_msleep(nng_duration msec);
+```
+
+## DESCRIPTION
+
+The `nng_msleep()` blocks the caller for at least _msec_ milliseconds.
+
+> [!NOTE]
+> This function may block for longer than requested.
+> The actual wait time is determined by the capabilities of the
+> underlying system.
+
+## SEE ALSO
+
+[nng_sleep_aio](nng_sleep_aio.md),
+[nng_clock](nng_clock.md)
diff --git a/docs/reference/src/api/util/nng_strdup.md b/docs/reference/src/api/util/nng_strdup.md
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+# nng_strdup
+
+## NAME
+
+nng_strdup --- duplicate string
+
+## SYNOPSIS
+
+```c
+#include <nng/nng.h>
+
+char *nng_strdup(const char *src);
+```
+
+## DESCRIPTION
+
+The `nng_strdup()` duplicates the string _src_ and returns it.
+
+This is logically equivalent to using [`nng_alloc()`](nng_alloc.md)
+to allocate a region of memory of `strlen(s) + 1` bytes, and then
+using `strcpy()` to copy the string into the destination before
+returning it.
+
+The returned string should be deallocated with
+[`nng_strfree()`](nng_strfree.md), or may be deallocated using the
+[`nng_free()`](nng_free.md) using the length of the returned string plus
+one (for the `NUL` terminating byte).
+
+> [!IMPORTANT]
+> Do not use the system `free()` or similar functions to deallocate
+> the string, since those may use a different memory arena!
+
+## RETURN VALUES
+
+This function returns the new string on success, and `NULL` on failure.
+
+## ERRORS
+
+No errors are returned, but a `NULL` return value should be
+treated the same as `NNG_ENOMEM`.
+
+## SEE ALSO
+
+[nng_alloc.md](nng_alloc.md),
+[nng_free.md](nng_free.md),
+[nng_strfree.md](nng_strfree.md)
diff --git a/docs/reference/src/api/util/nng_strfree.md b/docs/reference/src/api/util/nng_strfree.md
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+# nng_strfree
+
+## NAME
+
+nng_strfree --- free memory
+
+## SYNOPSIS
+
+```c
+#include <nng/nng.h>
+
+void nng_strfree(char *str);
+```
+
+## DESCRIPTION
+
+The `nng_strfree()` function deallocates the string _str_.
+This is equivalent to using [`nng_free()`](nng_free.md) with
+the length of _str_ plus one (for the `NUL` terminating byte) as
+the size.
+
+> [!IMPORTANT]
+> This should only be used with strings that were allocated
+> by [`nng_strdup()`](nng_strdup.md) or [`nng_alloc()`](nng_alloc.md).
+> In all cases, the allocation size of the string must be the same
+> as `strlen(__str__) + 1`.
+
+> [!IMPORTANT]
+> Consequently, if the a string created with
+> [`nng_strdup()`](nng_strfree.md) is modified to be shorter, then
+> it is incorrect to call this function.
+> (The [`nng_free()`](nng_Free.md) function can be used instead in that
+> case, using the length of the original string plus one for the size.)
+
+## SEE ALSO
+
+[nng_alloc](nng_alloc.md),
+[nng_free](nng_free.md),
+[nng_strdup](nng_strdup.md)