Talvez deva tentar algumas variações de ortografia:
research systems » research synthesis (Expandir a Pesquisa)
mental research » dental research (Expandir a Pesquisa), central research (Expandir a Pesquisa), neonatal research (Expandir a Pesquisa)
systems dis » systems disk (Expandir a Pesquisa), systems tdis (Expandir a Pesquisa), systems dss (Expandir a Pesquisa)
cent nerve » bent nerve (Expandir a Pesquisa), crest nerve (Expandir a Pesquisa), can nerve (Expandir a Pesquisa)
nerve cnat » nerve cat (Expandir a Pesquisa), nerve canal (Expandir a Pesquisa), nerve can (Expandir a Pesquisa)
nerve cn » nerve can (Expandir a Pesquisa), nerve c (Expandir a Pesquisa), nerve cat (Expandir a Pesquisa)
j mental » j mehta (Expandir a Pesquisa), j mena (Expandir a Pesquisa), j mentz (Expandir a Pesquisa)
a cent » a cena (Expandir a Pesquisa), a cenp (Expandir a Pesquisa), a center (Expandir a Pesquisa)
i cent » i cento (Expandir a Pesquisa), ai cent (Expandir a Pesquisa), ii cent (Expandir a Pesquisa)
cn dis » en dis (Expandir a Pesquisa), nn dis (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: (((( a cent nerve cnat dis ) or ( i cent nerve cn dis ))) or ( j mental research systems dis ))~.
• Se usar operadores Booleanos, por favor insira-os com letras MAIÚSCULAS: (((( a cent nerve cnat dis ) OR ( i cent nerve cn dis ))) OR ( j mental research systems dis )).
• Se adicionar um carácter universal pode recuperar variações da palavra pesquisada: (((( a cent nerve cnat dis ) or ( i cent nerve cn dis ))) or ( j mental research systems dis ))*.