Further (OR) Farther :  Both these are the comparative forms of ‘ Far ‘.  Further means ‘ more, additional or more distance’.  But  ‘ Farther ‘ refers only to distance.

Examples.

• We will make a decision on getting further details . ( NOT farther details.)
• It’s a long walk from here , further than I thought. ( OR farther than….)
• I can’t walk any farther. (OR any further)
• We must get further information. (NOT farther)
• We don’t want to go further into the matter.(NOT farther)
• The examination stands postponed until further notice.(NOT farther notice)