Talvez deva tentar algumas variações de ortografia:
research systems » research synthesis (Expandir a Pesquisa)
mehta research » meta research (Expandir a Pesquisa), beta research (Expandir a Pesquisa), feta research (Expandir a Pesquisa)
letter nurse » letter nursing (Expandir a Pesquisa), letter name (Expandir a Pesquisa)
benth serve » bent nerve (Expandir a Pesquisa), both serve (Expandir a Pesquisa), benth leaves (Expandir a Pesquisa)
systems di » systems do (Expandir a Pesquisa), systems de (Expandir a Pesquisa), systems d (Expandir a Pesquisa)
j letter » bj letter (Expandir a Pesquisa), cj letter (Expandir a Pesquisa), j letters (Expandir a Pesquisa)
nurse nn » nurse anne (Expandir a Pesquisa), nurse can (Expandir a Pesquisa), nurse apn (Expandir a Pesquisa)
i benth » l benth (Expandir a Pesquisa), ex benth (Expandir a Pesquisa)
serve c » serve _ (Expandir a Pesquisa), serve a (Expandir a Pesquisa), serve w (Expandir a Pesquisa)
k mehta » a mehta (Expandir a Pesquisa), _ mehta (Expandir a Pesquisa)
nn dis » en dis (Expandir a Pesquisa)
c dis » c dias (Expandir a Pesquisa), c disc (Expandir a Pesquisa), c dos (Expandir a Pesquisa)

You can also try:

• Europeana
• Digital Public Library of America
• CORE

Pode obter mais resultados ajustando a pesquisa.

• Performing a fuzzy search may retrieve terms with similar spellings: (((( j letter nurse nn dis ) or ( i benth serve c dis ))) or ( k mehta research systems di ))~.
• Se usar operadores Booleanos, por favor insira-os com letras MAIÚSCULAS: (((( j letter nurse nn dis ) OR ( i benth serve c dis ))) OR ( k mehta research systems di )).
• Se adicionar um carácter universal pode recuperar variações da palavra pesquisada: (((( j letter nurse nn dis ) or ( i benth serve c dis ))) or ( k mehta research systems di ))*.