Do not type accents in your searches. The data provided by the Instituto Nacional de Estatística omits them. So for example, a search for CASAS will yield results covering both Casas and Cásas.
2. To search for compound surnames, type an underline character (_) between elements. For example, to find Fernández Da Ponte, type FERNANDEZ_DA_PONTE. The same rule applies to names starting with a preposition such as DA_PONTE.
Asterisks and question marks may be used as wildcards in searches. An asterisk stands for any series of characters at the beginning or end of a string, e.g. a search for <PERE*> will return surnames that begin with PER- (such as PERE, PEREA, PEREDA, PEREZ, etc.). A question mark stands for a single character: a search for <SANCHE?> returns names of seven characters that begin with SANCHE- (e.g. SANCHEL, SANCHES, SANCHEZ).
4. Remember that a surname may have various spellings. Only names spelt exactly as in the census will be returned. Castilianized forms, and those spelt with or without an <h>, or with either a <b> or a <v> e.g. TEIXEIRO/TEIJEIRO, AIRA/AYRA, ERMIDA/HERMIDA, RIBEIRA /RIVEIRA) are counted as different names. To view all results for TEIXEIRO, TEIJEIRO and TEIGEIRO together, doing a search on TEI?EIRO will cause all these to be plotted together of these on one map. At the bottom-left, it will say “Surnames like TEI?EIRO″.