Suggestions for required

The following packages have something in common with the package required. The packages are ordered in decreasing similarity.

Package plainmisc: Miscellaneous contributed macros for plain TeX
Package obsolete: A tree holding obsolete software
Package treesvr: Tree macros
Package qobitree: LaTeX macros for typesetting trees
Package syntrace: Labels for tracing in a syntax tree
Package latex-tools: The LaTeX standard tools bundle
Package latex-cyrillic: Support for Cyrillic fonts in LaTeX
Package amslatex: Mathematical enhancements for LaTeX
Package adtrees: Macros for drawing adpositional trees
Package dirtreex: Directory tree rendering for LaTeX with TikZ
Package dyntree: Construct Dynkin tree diagrams
Package familytree: Draw family trees
Package xytree: Tree macros using XY-Pic
Package xyling: Draw syntactic trees, etc., for linguistics literature, using xy-pic
Package ecltree: Trees using epic and eepic macros
Package rrgtrees: Linguistic tree diagrams for Role and Reference Grammar (RRG) with LaTeX
Package synttree: Typeset syntactic trees
Package williams: Miscellaneous macros by Peter Williams
Package lingtrees: Linguistics trees preprocessor and macros
Package trig: Simple trigonometric functions
Package latex-graphics: The LaTeX standard graphics bundle
Package latex-firstaid: First aid for external LaTeX files and packages that need updating
Package amstext: Typeset text fragments in mathematics
Package color: Colour control for LaTeX documents
Package grfguide: LaTeX standard graphics and color packages documentation
Package multicol: Intermix single and multiple columns
Package tabularx: Tabulars with adjustable-width columns
Package testmath: Examples of the AMS-LaTeX package
Package amsopn: Typeset mathematical operator names
Package l3docstrip: Strip documentation in LaTeX3 source
Package keyval: Process key=value schemes