diff --git a/API_reference.py b/API_reference.py
index 075d94d..eed750a 100644
--- a/API_reference.py
+++ b/API_reference.py
@@ -69,9 +69,9 @@ green_ii_n = guan.green_function_ii_n(green_ii_n_minus, green_in_n_minus, h01, g
 transfer = guan.transfer_matrix(fermi_energy, h00, h01)
 right_lead_surface, left_lead_surface = guan.surface_green_function_of_lead(fermi_energy, h00, h01)
 right_self_energy, left_self_energy, gamma_right, gamma_left = guan.self_energy_of_lead(fermi_energy, h00, h01)
-right_self_energy, left_self_energy, gamma_right, gamma_left = self_energy_of_lead_with_h_LC_and_h_CR(fermi_energy, h00, h01, h_LC, h_CR)
+right_self_energy, left_self_energy, gamma_right, gamma_left = guan.self_energy_of_lead_with_h_LC_and_h_CR(fermi_energy, h00, h01, h_LC, h_CR)
 self_energy, gamma = guan.self_energy_of_lead_with_h_lead_to_center(fermi_energy, h00, h01, h_lead_to_center)
-green, gamma_right, gamma_left = green_function_with_leads(fermi_energy, h00, h01, h_LC, h_CR, center_hamiltonian)
+green, gamma_right, gamma_left = guan.green_function_with_leads(fermi_energy, h00, h01, h_LC, h_CR, center_hamiltonian)
 
 # calculate density of states    # Source code: https://py.guanjihuan.com/calculate_density_of_states
 total_dos = guan.total_density_of_states(fermi_energy, hamiltonian, broadening=0.01)