The structure of HVOR ANNAN things is generally an NP inside which HVOR has its own bare NP. This may not be a good analysis but it allows us to enforce case agreement inside NPs (as opposed to not having hvor project an NP).
(NP (NP (Q-N hvor)) (OTHER-A annan))
HVOR HJÁ ÖÐRUM etc.
For phrases like hvor hjá öðrum 'each with the other' treat the whole thing as NP-ADV. This parse is used *only* where *neither* "hvor" or "öðrum" are an argument of the verb *and* "öðrum" is inside a PP.
(NP-ADV (NP (Q-N hvor-hvor)) (PP (P hjá-hjá) (NP (OTHER-D öðrum-annar))))
More examples of this sort:
HVORT AÐ ÖÐRU (HVER AÐ ÖÐRUM, HVERT AÐ ÖÐRU, HVOR AÐ ÖÐRUM)
( (IP-MAT (VBPI hlaupa-hlaupa) (NP-SBJ (PRO-N þau-það)) (ADVP-TMP (ADV nú-nú)) (Q-N bæði-bæði) (ADVP-TMP (ADV jafnsnemma-jafnsnemma)) (NP-ADV (NP (Q-N hvort-hvor)) (PP (P að-að) (NP (OTHER-D öðru-annar))))))
Examples like stræti úr stræti, hring eftir hring are treated the same. See NP-ADV.
HVOR ANNAR / HVOR ÖÐRUM as NP-OB1
When "(hvor) öðrum" is clearly the object (or "hvor" is ambiguous between being part of the object or a floated quantifier) and "hvor" and "öðrum" appear adjacent, they are grouped together as an NP constituent, inside which hvor has its own bare NP, with the appropriate clause-level argument label, as below. NOTE: This is done regardess of the case-marking of "hvor".
( (IP-MAT (NP-SBJ (PRO-N þeir-hann)) (VBDI rituðu-rita) (NP-TMP (NS-D stundum-stundum)) (NP-OB1 (NP (Q-N hvor-hvor)) (OTHERS-D öðrum-annar)))
HVOR ANNAR / HVOR ÖÐRUM as PP complement
When "(hvor) öðrum" is clearly the object of a preposition and "hvor" and "öðrum" appear adjacent, they are grouped together as a bare NP and under that hvor has its own bare NP.
(PP (P við) (NP (NP (Q-N hvor-hvor)) (OTHER-A annan-annar)))
HVOR ANNAR / HVOR ÖÐRUM as NP-ADV
If *neither* "hvor" or "öðrum" are an argument of the verb but there is no PP involved:
(NP-ADV (NP (Q-N hvor-hvor)) (OTHERS-D öðrum-annar))
SITT ORÐ HVOR
(CP-THT-PRN-1 (C að-að) (IP-SUB (IP-SUB (NP-SBJ (PRO-N hann-hann)) (VBDI þóttist-þykja) (IP-INF (VB sjá-sjá) (NP-OB1 (NS-A hrafna-hrafn) (NUM-A tvo-tveir)))) (CONJP (CONJ og-og) (IP-SUB (NP-SBJ *pro*) (VBDI kváðu-kveða) (NP-OB1 (D-A þetta-þessi)) (NP-ADV (NP (NP-POS (PRO-A sitt-sinn)) (N-A orð-orð)) (NP (Q-N hvor-hvor)))))))