Technique and description | Command | Example |

All known synonyms and spellings of key words | Doubly robust regression could also be referred to as doubly robust estimate | |

Replace up to one character in the word—allows alternative spellings to be included. | ? | Mendelian randomi?ation would include Mendelian randomisation and Mendelian randomization |

Truncation command—used to acknowledge and capture alternative endings to words. | * | Inverse probability weight* would additionally search for inverse probability weights and inverse probability weighting |

Boolean logic operators—used to either: (a) identify results with at least one of the search terms present; and, (b) to combine results of different search terms. | “OR” “AND” | Conduct problem* OR conduct disorder* would retrieve articles that have either terms.Conduct problem* AND causal* would only retrieve articles that have both terms. |

Proximity operators—used to identify words within a specified distance of each other. | adj3 | Balancing adj3 covariate would identify articles whereby “balancing” and “covariate” are within three words of each other. |