Include header files

[ianmingwu]

I am complete new to GNUstep. By following the example at 
http://www.nongnu.org/gstutorial/en/ch09.html now I am able to compile and 
execute hello world program. However, when trying to include other header files 
(impl is cpp), make complains 

  fatal error: One.h: No such file or directory

My GNUmakefile looks like  (sample is borrowed from 'GNUstep Makefile Package') 
below. Also `ls ../One` can find One.h header. Is any additional config 
required? Or what is the right way to include the header files?  

Thanks for help 

include $(GNUSTEP_MAKEFILES)/common.make
APP_NAME = Test
LIBRARY_NAME = One
One_HEADER_FILES_DIR = ../One
One_HEADER_FILES = One.h
Test_OBJC_FILES = main.m z
Test_RESOURCE_FILES =
include $(GNUSTEP_MAKEFILES)/application.make


main.m looks like 
#include <stdio.h>
#include <AppKit/AppKit.h>
#include "One.h"

int main(int argc, char *argv[])
{
    return NSApplicationMain(argc, (const char **)argv);
}