Yet another undefined symbol

Good day,
in order to become familiar with the MCBSTR9 I first modified the Blinky program. That wasn't too difficult. But stage two was to write the same program using my own syntax and referring to the ST Software Library (www.st.com/.../12238.pdf). Done this, I yet only tried to set up the GPIO7:

#include<91x_map.h>
#include<91x_GPIO.h>

int main(void){
  GPIO_InitTypeDef GPIO_Initialiser;
  GPIO_Initialiser.GPIO_Pin = GPIO_Pin_7;
  GPIO_Initialiser.GPIO_Direction = GPIO_PinOutput;
  GPIO_Initialiser.GPIO_Type = GPIO_Type_PushPull;
  GPIO_Initialiser.GPIO_IPConnected = GPIO_IPConnected_Disable;
  GPIO_Initialiser.GPIO_Alternate = GPIO_InputAlt1;
  GPIO_Init(GPIO7, &GPIO_Initialiser);
}

Compiling states:
Blinky2.axf: Error: L6218E: Undefined symbol GPIO_Init (referred from blinky2.o).

As you might guess, my experience in both uCs and C is approaching nil.

Helpful input appreciated.

Cheers
Nik