External reference URLs (PDLC approach guides)

Curated list of https targets cited in PDLC approach guides (blueprint) and in PDLC ↔ SDLC bridge. When you change a URL in Markdown, update the matching approach guide's "Authoritative sources" section.

Each row includes an executive summary: what the link is and why this blueprint points to it, so readers can decide whether to open it.

Product management & discovery

Topic URL Executive summary (why it's linked here)
Marty Cagan — SVPG (Inspired / Empowered) https://www.svpg.com/inspired-how-to-create-tech-products-customers-love/ Foundational text on modern product management: product trio, discovery, empowered teams. Philosophical anchor for PDLC thinking about outcomes over outputs.
Marty Cagan — Dual-Track Agile https://www.svpg.com/dual-track-agile/ Origin framing for running discovery and delivery in parallel — defines why the product trio co-owns discovery alongside engineering delivery.
SVPG — Product Discovery https://www.svpg.com/product-discovery/ Collection of articles on discovery practices — risk assessment, opportunity assessment, prototyping — from the SVPG team.
Teresa Torres — Continuous Discovery Habits https://www.producttalk.org/2021/08/continuous-discovery-habits/ Practical framework for weekly discovery: opportunity solution trees, interview cadence, assumption mapping. Operationalizes PDLC P1–P2 as ongoing practice.
Teresa Torres — Opportunity Solution Trees https://www.producttalk.org/2023/12/opportunity-solution-trees/ Canonical source for the OST framework — visual structure connecting outcomes → opportunities → solutions → experiments.
Product Talk (blog) https://www.producttalk.org/ Blog and community from Teresa Torres — ongoing articles on discovery, experimentation, and product trio practices.
Melissa Perri — Escaping the Build Trap https://melissaperri.com/book Diagnosis and cure for organizations that ship features without validating outcomes — directly addresses the "SDLC without PDLC" anti-pattern.
Mind the Product https://www.mindtheproduct.com/ Community hub for product management: conferences, articles, and frameworks — neutral background for PDLC vocabulary.
Product School — Resources https://productschool.com/blog Practitioner content on product management — OSTs, discovery, metrics, team structures.

Lean Startup & experimentation

Topic URL Executive summary (why it's linked here)
Eric Ries — The Lean Startup http://theleanstartup.com/ Canonical text defining Build-Measure-Learn, MVP, validated learning, pivot/persevere. The reference for hypothesis-driven product development.
Steve Blank — Customer Development https://steveblank.com/category/customer-development/ Precursor framework to Lean Startup: Customer Discovery → Validation → Creation → Building. Business-model-validation layer.
Ash Maurya — Running Lean / Lean Stack https://leanstack.com/running-lean-book Practitioner playbook for applying Lean Startup — Lean Canvas, experiment design, metrics that matter.
Jeff Gothelf — Lean UX https://www.jeffgothelf.com/lean-ux-book/ UX + Lean Startup integration — hypotheses, experiments, outcomes in Agile teams. Bridges design practice with delivery.
Jeff Patton — Dual Track Development https://www.jpattonassociates.com/dual-track-development/ Practical guidance on separating learning work from building work — visual models for dual-track implementation.

Design Thinking

Topic URL Executive summary (why it's linked here)
IDEO — Design Thinking https://designthinking.ideo.com/ Origin framework — Empathize, Define, Ideate, Prototype, Test. Defines human-centered design principles used in PDLC P1–P2.
Stanford d.school https://dschool.stanford.edu/ Academic anchor for Design Thinking education — process guides, teaching materials, and the "bootcamp bootleg" toolkit.
British Design Council — Double Diamond https://www.designcouncil.org.uk/our-resources/the-double-diamond/ Double Diamond model — canonical visualization of diverge/converge across problem and solution spaces.
Nielsen Norman Group — Design Thinking https://www.nngroup.com/articles/design-thinking/ Evidence-based practitioner summary of when Design Thinking works and its limitations.

Agile product delivery (vendor context)

Topic URL Executive summary (why it's linked here)
Atlassian — Product development https://www.atlassian.com/agile/product-management/product-development Practitioner overview of product development in an Agile context — complements Forge’s PDLC ↔ SDLC bridge for software teams.

Stage-Gate & governance

Topic URL Executive summary (why it's linked here)
Stage-Gate International https://www.stage-gate.com/ Official Stage-Gate body of knowledge — Robert Cooper's framework, 5th-generation updates, research. Authority for gate criteria and stage definitions.
Stage-Gate — Discovery-to-launch process https://www.stage-gate.com/about/stage-gate-innovation-performance-framework/discovery-to-launch-process/ Discovery-to-launch framing from Stage-Gate International — aligns with gated NPD vocabulary used alongside Forge P1–P6.
5th-Generation Stage-Gate Model https://www.stage-gate.com/about/5th-generation-stage-gate-model/ Current evolution: iterative stages, Agile integration, lean gates, adaptive governance. Addresses historical rigidity criticism.
PDMA — Product Development and Management Association https://community.pdma.org/ Practitioner community for product development — research, benchmarking, and Stage-Gate updates from Robert Cooper.

Product lifecycle & growth

Topic URL Executive summary (why it's linked here)
ProductPlan — Product development cycle https://www.productplan.com/glossary/product-development-cycle/ Definition overview of the product development cycle — helps teams compare generic phase language to Forge P1–P6 without claiming one global standard.
ProductPlan — Product Lifecycle https://productplan.com/glossary/product-lifecycle/ Clear overview of lifecycle stages (Introduction, Growth, Maturity, Decline) with strategic implications. Starting reference for PLM.
ProductPlan — End-of-Life https://productplan.com/learn/how-to-end-of-life-product/ Practical checklist for product retirement — communications, migration, support wind-down. Informs P6 sunset planning.
Product Marketing Alliance — Sunsetting https://productmarketingalliance.com/how-to-sunset-product-complete-guide-examples/ Complete guide with real examples of product sunset strategies — phased approach, stakeholder management.
Reforge — Growth Series https://www.reforge.com/growth-series Growth frameworks for post-launch: acquisition, activation, retention, revenue, referral. Deepens P5 Grow.
DORA — State of DevOps https://dora.dev/ Delivery metrics research (DORA four key metrics) — the SDLC side of the metrics comparison in the bridge document.

Quick verification (maintainers)

From a shell, expect HTTP 200 (some sites return 301 then 200 when following redirects):

urls=(
  https://www.svpg.com/inspired-how-to-create-tech-products-customers-love/
  https://www.producttalk.org/2021/08/continuous-discovery-habits/
  http://theleanstartup.com/
  https://designthinking.ideo.com/
  https://www.stage-gate.com/
  https://www.stage-gate.com/about/stage-gate-innovation-performance-framework/discovery-to-launch-process/
  https://productplan.com/glossary/product-lifecycle/
  https://www.productplan.com/glossary/product-development-cycle/
  https://www.atlassian.com/agile/product-management/product-development
  https://dora.dev/
  https://www.designcouncil.org.uk/our-resources/the-double-diamond/
)
for u in "${urls[@]}"; do
  printf '%s ' "$(curl -sS -o /dev/null -w '%{http_code}' -L --max-time 15 "$u")"
  echo "$u"
done

Expand the array with any new links before merging doc changes.