Task: Text Categorization
Input (English): Tsakalidis represented these data structures as a BB-alpha tree, which allows one to find the ancestor relationship of elements in Big O of 1 time. Maurer's Shadow Algorithm uses a dynamic version of one of these data structures to speed up simulations. CDR coding is a representation for these them in LISP, and multiple pieces of information are stored in each element in the (*) unrolled variant of them. Their ends may be demarcated by sentinel nodes, while circular ones have the final node point to the initial one. For 10 points, name these data structures which come in "singly" and "doubly" versions, whose nodes each contains a pointer to the next and/or previous node.
Output (English): Science