Update 6_reference_guide.rst
Update 6_reference_guide.rst

Stratio/crossdata,hdominguez1989/Crossdata,gserranojc/Crossdata,luismcl/crossdata,compae/Crossdata,pmadrigal/Crossdata,gserranojc/Crossdata,jjlopezm/crossdata,jjlopezm/crossdata,miguel0afd/crossdata,compae/Crossdata,pmadrigal/Crossdata,darroyocazorla/crossdata,hdominguez1989/Crossdata,luismcl/crossdata,miguel0afd/crossdata,Stratio/crossdata,darroyocazorla/crossdata