This are the internal fieldnames and their meaning of the 1.4 addressbook:
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id                   => Contact ID
tid                  => Typ
owner                => Addressbook
private              => private
cat_id               => Category
n_prefix             => prefix
n_given              => first name
n_middle             => middle name
n_family             => last name
n_suffix             => suffix
n_fn                 => full name
n_fileas             => own sorting
bday                 => birthday
org_name             => Company
org_unit             => Department
title                => Title
role                 => Role
assistent            => Assistent
room                 => Room
adr_one_street       => street business
adr_one_street2      => address line 2 business
adr_one_locality     => city business
adr_one_region       => state business
adr_one_postalcode   => zip code business
adr_one_countryname  => country business
label                => label
adr_two_street       => street private
adr_two_street2      => address line 2 private
adr_two_locality     => city private
adr_two_region       => state private
adr_two_postalcode   => zip code private
adr_two_countryname  => country private
tel_work             => work phone
tel_cell             => mobile phone
tel_fax              => fax business
tel_assistent        => assistent phone
tel_car              => car phone
tel_pager            => pager
tel_home             => home phone
tel_fax_home         => fax private
tel_cell_private     => mobile phone private
tel_other            => other phone
tel_prefer           => preferred phone
email                => email business
email_home           => email private
url                  => url business
url_home             => url private
freebusy_uri         => Freebusy URI
calendar_uri         => Calendar URI
note                 => note
tz                   => time zone
geo                  => geo
pubkey               => public key
created              => created
creator              => created by
modified             => last modified
modifier             => last modified by
jpegphoto            => photo
