To interpret LAS file

Hello,

I am going to interpret LAS file. I would like to get some help.

1) For Bulk denisty, RHOB will be used. There is sometimes DRHO (Density Correction). How can I use DRHO? This should be added to RHOB?

2) for one well, many logs for DT (Sonic) and DTS (Shear Sonic) exist. (such as DT1, DT2, DT3... DTS1, DTS2, DTS3, ... etc.) I need to get Compressive velocity and shear velocity. How can I choose for these?

3) When there is no shear velocity, what correlation can be used to estimate it using DT?

Thank you.