In their description of isoglosses , they 
( In ( ( their description ) ( of ( ( isoglosses , ) they ) ) ) )
(ROOT (PP (IN In) (NP (NP (PRP$ their) (NN description)) (PP (IN of) (NP (NP (NNS isoglosses)) (, ,) (NP (PRP they)))))))
They omit any description of isoglosses.
( They ( ( omit ( ( any description ) ( of isoglosses ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBP omit) (NP (NP (DT any) (NN description)) (PP (IN of) (NP (NNS isoglosses))))) (. .)))