Talvez deva tentar algumas variações de ortografia:
natural mixed » national mixed (Expandir a Pesquisa)
mixed problem » wicked problem (Expandir a Pesquisa), based problem (Expandir a Pesquisa)
process spot » process split (Expandir a Pesquisa), process show (Expandir a Pesquisa), process sao (Expandir a Pesquisa)
problem srep » problem sleep (Expandir a Pesquisa), problem srflp (Expandir a Pesquisa), problem set (Expandir a Pesquisa)
ntd process » npd process (Expandir a Pesquisa), need process (Expandir a Pesquisa), bed process (Expandir a Pesquisa)
adv natural » aav natural (Expandir a Pesquisa), hiv natural (Expandir a Pesquisa), hpv natural (Expandir a Pesquisa)
ama neurol » acad neurol (Expandir a Pesquisa), adv neurol (Expandir a Pesquisa), ann neurol (Expandir a Pesquisa)
neurol ntd » neuronal nt2 (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: (( ama neurol ntd process spot ) or ( adv natural mixed problem srep ))~.
• Se usar operadores Booleanos, por favor insira-os com letras MAIÚSCULAS: (( ama neurol ntd process spot ) OR ( adv natural mixed problem srep )).
• Se adicionar um carácter universal pode recuperar variações da palavra pesquisada: (( ama neurol ntd process spot ) or ( adv natural mixed problem srep ))*.