-->  To keep abreast of    -->  To keep at    -->  To keep at    -->  To keep out of sight    -->  To keep to oneself    -->  To keep ... to oneself    -->  To keep up with    -->  A kind (sort) of (a) ...    -->  To be two of a kind    -->  Nothing of the kind    -->  Before you know it    -->  How do I know?    -->  To be in the know    -->  To know full well (only too well)    -->  To make known