Talvez deva tentar algumas variações de ortografia:
central nerve » ventral nerve (Expandir a Pesquisa), central nervous (Expandir a Pesquisa), central neural (Expandir a Pesquisa)
current valve » current value (Expandir a Pesquisa), recurrent valve (Expandir a Pesquisa), current values (Expandir a Pesquisa)
valve system » value system (Expandir a Pesquisa), drive system (Expandir a Pesquisa), nerve system (Expandir a Pesquisa)
system das » system dias (Expandir a Pesquisa), systems das (Expandir a Pesquisa), system des (Expandir a Pesquisa)
bent nerve » absent nerve (Expandir a Pesquisa), mental nerve (Expandir a Pesquisa), dental nerve (Expandir a Pesquisa)
i central » coli central (Expandir a Pesquisa), hemi central (Expandir a Pesquisa)
nerve fat » nerve fatty (Expandir a Pesquisa), nerves fate (Expandir a Pesquisa), nerve flap (Expandir a Pesquisa)
case di » case dti (Expandir a Pesquisa), case d (Expandir a Pesquisa), case de (Expandir a Pesquisa)
j bent » j benet (Expandir a Pesquisa), j bento (Expandir a Pesquisa), j bena (Expandir a Pesquisa)

You can also try:

• Europeana
• Digital Public Library of America
• CORE

Pode obter mais resultados ajustando a pesquisa.

• "As palabras AND, OR e NOT podem gerar pesquisas incorrectas; tente utilizar aspas": "(((( i central nerve fat diet ) OR ( i current valve system das ))) OR ( j bent nerve case di ))~".
• Se adicionar um carácter universal pode recuperar variações da palavra pesquisada: (((( i central nerve fat diet ) OR ( i current valve system das ))) OR ( j bent nerve case di ))*.