class AliITSUTrackerSA: public AliTracker

 This default constructor needs to be provided

 The copy constructor is protected

 d-tor

 init with external reconstructor

 This is the main tracking function
 The clusters must already be loaded

 Here, we implement the Kalman smoother ?
 The clusters must be already loaded

 Some final refit, after the outliers get removed by the smoother ?
 The clusters must be loaded

 This function reads the ITSU clusters from the tree,
 sort them, distribute over the internal tracker arrays, etc

 This function unloads ITSU clusters from the RAM

 Make associations between two points on adjacent layers within an azimuthal window.
 Under consideration:
 - track parameter estimation using the primary vertex position
 To do:
 - last iteration

 Set the initial guess on track kinematics for propagation.
 Assume at least 3 points available

 refit track till radius rDest.
 if stopCond<0 : propagate till last cluster then stop
 if stopCond==0: propagate till last cluster then try to go till limiting rDest, don't mind if fail
 if stopCond>0 : rDest must be reached

 The clList should provide the indices of clusters at corresponding layer (as stored in the layer
 TClonesArray, with convention (allowing for up to 2 clusters per layer due to the overlaps):
 if there is a cluster on given layer I, then it should be stored at clInfo[2*I-1]
 if there is an additional cluster on this layer, it goes to clInfo[2*I]
 -1 means no cluster

 propagate seed to given x applying material correction if requested

 transport track from layerFrom to the entrance of layerTo or to rLim (if>0), wathever is closer

 transport track from layerFrom to the entrance of layerTo but do not pass control parameter X

 go to the exit from lr in direction dir, applying material corrections in steps specific for this layer
 If check is requested, do this only provided the track has not exited the layer already

 go to the entrance of lr in direction dir, w/o applying material corrections.
 If check is requested, do this only provided the track did not reach the layer already

 Other protected functions
 (Sorting, labeling, calculations of "roads", etc)