$ grep -hr '^\*\*.*\*\*$' . | sort -u

**Circular References**
**Coercing Results**
**Conforming Algorithms**
**Delivery Agnostic**
**Escape Sequences**
**Explanatory Text**
**Field Ordering**
**First Class Documentation**
**Formal Specification**
**Interfaces Implementing Interfaces**
**Lexical Analysis & Syntactic Parse**
**Lookahead Restrictions**
**Non-Normative Portions**
**Parameterized Grammar Productions**
**Static Semantics**
**Supporting Subscriptions at Scale**

**Block Strings**
**Built-in Directives**
**Built-in Scalars**
**Custom Directives**
**Custom Scalars**
**Default Root Operation Type Names**
**Errors and Non-Null Fields**
**Event Streams**
**Input Coercion**
**Input Object**
**Merging Selection Sets**
**Nullable vs. Optional**
**Optionality and Lists**
**Reserved Names**
**Resolving Abstract Types**
**Result Coercion and Serialization**
**Result Coercion**
**Schema Introspection Schema**
**Schema Validation**
**Type Validation**

**Allowing optional variables when default values exist**
**Arguments are unordered**
**Byte order mark**
**Copyright notice**
**Directive order is significant**
**Error result format**
**Field errors**
**Input object fields are unordered**
**Query shorthand**
**Request errors**
**Type system evolution**

**Interface Spreads in implemented Interface Scope**
**Variable use within Fragments**

**Conformance**
**Constraints**
**Deprecation**
**Enum**
**Examples**
**Interface**
**Introduction**
**Licensing**
**List**
**Non-Null**
**Object**
**Scalar**
**Semantics**
**Union**
**Validation**