diff --git a/generic_data/Functions/functions.xml b/generic_data/Functions/functions.xml
index be8c221..94ec89f 100644
--- a/generic_data/Functions/functions.xml
+++ b/generic_data/Functions/functions.xml
@@ -89,17 +89,38 @@
         <new_kernel>alfvenVelocity</new_kernel>
     </function>
 
-    <!--<function name="fairfield70(,)" params="3" kind="physics">
-        <prompt>FAIRFIELD 1970 model of neutral sheet position Z = fairfield70(y_sm, z_sm, x_ss) 
+     <function name="perreault78()" params="3" kind="physics">
+        <info_brief>Perreault and Akasofu 1978 model u = perreault78(E_mag, B_mag, theta_p)</info_brief>
+        <new_kernel>perreault78</new_kernel>
+    </function>
+
+    <function name="newell2007(,)" params="3" kind="physics">
+        <info_brief>NEWELL et al 2007 solar wind-magnetosphere coupling function d_phi/d_t = newell2007(mu, B_mag, theta) </info_brief>
+        <new_kernel>newell2007</new_kernel>
+    </function>
+
+    <function name="fairfield70(,)" params="2" kind="physics">
+        <prompt>FAIRFIELD 1970 model of neutral sheet position Z = fairfield70(xyz_sm, x_ss) 
                where y_sm and z_sm  are the solar magnetospheric coordinates of the spacecraft 
-               and x_ss is geomagnetic latitude of the sun</prompt>
+               and x_ss is tilt angle</prompt>
 
-        <info_brief>FAIRFIELD 1970 model of neutral sheet position Z = fairfield70(y_sm, z_sm, x_ss) 
+        <info_brief>FAIRFIELD 1970 model of neutral sheet position Z = fairfield70(xyz_sm, x_ss) 
                where y_sm and z_sm  are the solar magnetospheric coordinates of the spacecraft 
-               and x_ss is geomagnetic latitude of the sun</info_brief>
+               and x_ss is tilt angle</info_brief>
         <new_kernel>fairfield70</new_kernel>
     </function>
 
+   <function name="fairfield80(,)" params="2" kind="physics">
+        <prompt>FAIRFIELD 1980 model of neutral sheet position Z = fairfield80(xyz_sm, x_ss)
+               where xyz_sm are the solar magnetospheric coordinates of the spacecraft
+               and x_ss is tilt angle</prompt>
+
+        <info_brief>FAIRFIELD 1980 model of neutral sheet position Z = fairfield80(xyz_sm, x_ss)
+               where xyz_sm are the solar magnetospheric coordinates of the spacecraft
+               and x_ss is tilt angle</info_brief>
+        <new_kernel>fairfield80</new_kernel>
+    </function>
+
     <function name="lopez90(,)" params="4" kind="physics">
         <prompt>
             Lopez 1990 model of magnetic latitude of the neutral sheet  MLAT = lopez90(Kp, phi, R, DTA)
@@ -112,7 +133,7 @@
             R is the radial distance in RE and DTA is the dipole tilt angle 
         </info_brief>
         <new_kernel>lopez90</new_kernel>
-    </function>-->
+    </function>
 
   <!--<function name="gsegsm_()" argv="vector" kind="amda">
       <prompt/>
--
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